US9602245B2  Transmitting apparatus and interleaving method thereof  Google Patents
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 US9602245B2 US9602245B2 US14/716,124 US201514716124A US9602245B2 US 9602245 B2 US9602245 B2 US 9602245B2 US 201514716124 A US201514716124 A US 201514716124A US 9602245 B2 US9602245 B2 US 9602245B2
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 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L1/00—Arrangements for detecting or preventing errors in the information received
 H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
 H04L1/0041—Arrangements at the transmitter end

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 G06F11/00—Error detection; Error correction; Monitoring
 G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
 G06F11/08—Error detection or correction by redundancy in data representation, e.g. by using checking codes
 G06F11/10—Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's
 G06F11/1004—Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's to protect a block of data words, e.g. CRC or checksum

 H—ELECTRICITY
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 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/03—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words
 H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
 H03M13/11—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits using multiple parity bits
 H03M13/1102—Codes on graphs and decoding on graphs, e.g. lowdensity parity check [LDPC] codes

 H—ELECTRICITY
 H03—BASIC ELECTRONIC CIRCUITRY
 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/03—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words
 H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
 H03M13/11—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits using multiple parity bits
 H03M13/1102—Codes on graphs and decoding on graphs, e.g. lowdensity parity check [LDPC] codes
 H03M13/1148—Structural properties of the code paritycheck or generator matrix
 H03M13/116—Quasicyclic LDPC [QCLDPC] codes, i.e. the paritycheck matrix being composed of permutation or circulant submatrices
 H03M13/1165—QCLDPC codes as defined for the digital video broadcasting [DVB] specifications, e.g. DVBSatellite [DVBS2]

 H—ELECTRICITY
 H03—BASIC ELECTRONIC CIRCUITRY
 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/25—Error detection or forward error correction by signal space coding, i.e. adding redundancy in the signal constellation, e.g. Trellis Coded Modulation [TCM]
 H03M13/253—Error detection or forward error correction by signal space coding, i.e. adding redundancy in the signal constellation, e.g. Trellis Coded Modulation [TCM] with concatenated codes

 H—ELECTRICITY
 H03—BASIC ELECTRONIC CIRCUITRY
 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/25—Error detection or forward error correction by signal space coding, i.e. adding redundancy in the signal constellation, e.g. Trellis Coded Modulation [TCM]
 H03M13/255—Error detection or forward error correction by signal space coding, i.e. adding redundancy in the signal constellation, e.g. Trellis Coded Modulation [TCM] with Low Density Parity Check [LDPC] codes

 H—ELECTRICITY
 H03—BASIC ELECTRONIC CIRCUITRY
 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/27—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes using interleaving techniques
 H03M13/2703—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes using interleaving techniques the interleaver involving at least two directions
 H03M13/2707—Simple rowcolumn interleaver, i.e. pure block interleaving

 H—ELECTRICITY
 H03—BASIC ELECTRONIC CIRCUITRY
 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/27—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes using interleaving techniques
 H03M13/2778—Interleaver using blockwise interleaving, e.g. the interleaving matrix is subdivided into submatrices and the permutation is performed in blocks of submatrices

 H—ELECTRICITY
 H03—BASIC ELECTRONIC CIRCUITRY
 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/27—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes using interleaving techniques
 H03M13/2792—Interleaver wherein interleaving is performed jointly with another technique such as puncturing, multiplexing or routing

 H—ELECTRICITY
 H03—BASIC ELECTRONIC CIRCUITRY
 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/61—Aspects and characteristics of methods and arrangements for error correction or error detection, not provided for otherwise
 H03M13/615—Use of computational or mathematical techniques
 H03M13/616—Matrix operations, especially for generator matrices or check matrices, e.g. column or row permutations

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L1/00—Arrangements for detecting or preventing errors in the information received
 H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
 H04L1/0056—Systems characterized by the type of code used
 H04L1/0057—Block codes

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L1/00—Arrangements for detecting or preventing errors in the information received
 H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
 H04L1/0056—Systems characterized by the type of code used
 H04L1/0057—Block codes
 H04L1/0058—Blockcoded modulation

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L1/00—Arrangements for detecting or preventing errors in the information received
 H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
 H04L1/0056—Systems characterized by the type of code used
 H04L1/0071—Use of interleaving

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L27/00—Modulatedcarrier systems
 H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
 H04L27/34—Amplitude and phasemodulated carrier systems, e.g. quadratureamplitude modulated carrier systems
 H04L27/36—Modulator circuits; Transmitter circuits

 H—ELECTRICITY
 H03—BASIC ELECTRONIC CIRCUITRY
 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/03—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words
 H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
 H03M13/13—Linear codes
 H03M13/15—Cyclic codes, i.e. cyclic shifts of codewords produce other codewords, e.g. codes defined by a generator polynomial, BoseChaudhuriHocquenghem [BCH] codes
 H03M13/151—Cyclic codes, i.e. cyclic shifts of codewords produce other codewords, e.g. codes defined by a generator polynomial, BoseChaudhuriHocquenghem [BCH] codes using error location or error correction polynomials
 H03M13/152—BoseChaudhuriHocquenghem [BCH] codes
Abstract
Description
This application claims priority from U.S. Provisional Application No. 62/001,168 field on May 21, 2014 and Korean Patent Application No. 1020150000672 filed on Jan. 5, 2015, the disclosures of which are incorporated herein by reference in their entirety.
1. Field
Apparatuses and methods consistent with exemplary embodiments relate to a transmitting apparatus which processes and transmits data, and an interleaving method thereof.
2. Description of the Related Art
In the 21st century informationoriented society, broadcasting communication services are moving into the era of digitalization, multichannel, wideband, and high quality. In particular, as high quality digital televisions, portable multimedia players and portable broadcasting equipment are increasingly used in recent years, there is an increasing demand for methods for supporting various receiving methods of digital broadcasting services.
In order to meet such demand, standard groups are establishing various standards and are providing a variety of services to satisfy users' needs. Therefore, there is a need for a method for providing improved services to users with high decoding and receiving performance.
Exemplary embodiments of the inventive concept may overcome the above disadvantages and other disadvantages not described above. However, it is understood that the exemplary embodiment are not required to overcome the disadvantages described above, and may not overcome any of the problems described above.
The exemplary embodiments provide a transmitting apparatus which can map a bit included in a predetermined bit group from among a plurality of bit groups of a low density parity check (LDPC) codeword onto a predetermined bit of a modulation symbol, and transmit the bit, and an interleaving method thereof.
According to an aspect of an exemplary embodiment, there is provided a transmitting apparatus which may include: an encoder configured to perform an LDPC encoding on input bits using a parity check matrix to generate an LDPC codeword comprising information word bits and parity bits; an interleaver configured to interleave the LDPC codeword; and a modulator configured to map the interleaved LDPC codeword onto a modulation symbol, wherein the modulator is further configured to map a bit included in a predetermined bit group from among a plurality of bit groups constituting the LDPC codeword onto a predetermined bit of the modulation symbol.
The parity check matrix may be formed of an information word submatrix and a parity submatrix. Each of the plurality of bit groups constituting the LDPC codeword may be formed of M number of bits. M may be a common divisor of N_{ldpc }and K_{ldpc }and may be determined to satisfy Q_{ldpc}=(N_{ldpc}−K_{ldpc})/M. In this case, Q_{ldpc }may be a cyclic shift parameter value regarding columns in a column group of the information word submatrix of the parity check matrix, N_{ldpc }may be a length of the LDPC codeword, and K_{ldpc }may be a length of the information word bits of the LDPC codeword.
The interleaver may include: a parity interleaver configured to interleave the parity bits of the LDPC codeword; a group interleaver configured to divide the parityinterleaved LDPC codeword into the plurality of bit groups and rearrange an order of the plurality of bit groups in bit group wise; and a block interleaver configured to interleave the plurality of bit groups the order of which is rearranged.
The group interleaver may be configured to rearrange the order of the plurality of bit groups in bit group wise by using Equation 21.
Here, in Equation 21, π(j) may be determined based on at least one of a length of the LDPC codeword, a modulation method, and a code rate.
In Equation 21, π(j) can be defined as Table 15, when a length of the LDPC codeword is 16200, the modulation method is 256QAM, and the code rate is 5/15.
The block interleaver may be configured to interleave by writing bits included in the plurality of bit groups in a plurality of columns in bit group wise in a column direction, and reading the plurality of columns in which the plurality of bit groups are written in bit group wise in a row direction.
The block interleaver may be configured to serially write, in the plurality of columns, bits included in at least some bit groups which are writable in the plurality of columns in bit group wise from among the plurality of bit groups, and divide bits included in bit groups other than the at least some bit groups in an area which is different from an area where the at least some bit groups are written in the plurality of columns in bit group wise.
The block interleaver may be configured to divide the plurality of columns, each including a plurality of rows, into a first part and a second part, write bits included in at least some bit groups in the first part such that bits included in a same bit group is written in a same column, and write bits included in at least one bit group other than the at least some bit groups in the second part.
The block interleaver may be configured to divide the plurality of columns into the first and second parts based on at least one of a number of the columns, a number of the bit groups constituting the LDPC codeword, and a number of bits constituting each of the bit groups.
If a number of bit groups constituting the LDPC codeword is an integer multiple of a number of the columns, the block interleaver may be configured to write all bits included in the bit groups serially in the plurality of columns without dividing the plurality of columns into the first and second parts.
According to an aspect of another exemplary embodiment, there is provided an interleaving method of a transmitting apparatus. The method may include: performing an LDPC encoding on input bits using a parity check matrix to generate an LDPC codeword comprising information word bits and parity bits; interleaving the LDPC codeword; and mapping the interleaved LDPC codeword onto a modulation symbol, wherein the mapping comprises mapping a bit included in a predetermined bit group from among a plurality of bit groups constituting the LDPC codeword onto a predetermined bit of the modulation symbol.
The parity check matrix may be formed of an information word submatrix and a parity submatrix. Each of the plurality of bit groups may be formed of M number of bits, and M may be a common divisor of N_{ldpc }and K_{ldpc }and may be determined to satisfy Q_{ldpc}=(N_{ldpc}−K_{ldpc})/M. In this case, Q_{ldpc }may be a cyclic shift parameter value regarding columns in a column group of the information word submatrix of the parity check matrix, N_{ldpc }may be a length of the LDPC codeword, and K_{ldpc }may be a length of the information word bits of the LDPC codeword.
The interleaving may include: interleaving parity bits of the LDPC codeword; dividing the parityinterleaved LDPC codeword into the plurality of bit groups and rearranging an order of the plurality of bit groups in bit group wise; and interleaving the plurality of bit groups the order of which is rearranged.
The rearranging an order of the plurality of bit groups in bit group wise may include rearranging the order of the plurality of bit groups in bit group wise by using the Equation 21.
In Equation 21, π(j) may be determined based on at least one of a length of the LDPC codeword, a modulation method, and a code rate.
In Equation 21, when a length of the LDPC codeword is 16200, the modulation method is 256QAM, and the code rate is 5/15, π(j) may be defined as Table 15.
The interleaving the plurality of bit groups may include interleaving by writing bits included in the plurality of bit groups in a plurality of columns in bit group wise in a column direction, and reading each row of the plurality of columns in which the bits included in the plurality of bit groups are written in bit group wise in a row direction.
The interleaving the plurality of bit groups may include serially writing, in the plurality of columns, bits included in at least some bit groups which are writable in the plurality of columns in bit group wise from among the plurality of bit groups, and dividing bits included in bit groups other than the at least some bit groups in an area which is different from an area where the at least some bit groups are written in the plurality of columns in bit group wise.
The interleaving the plurality of bit groups may include: dividing the plurality of columns, each including a plurality of rows, into a first part and a second part; and writing bits included in at least some bit groups in the first part such that bits included in a same bit group is written in a same column, and writing bits included in at least one bit group other than the at least some bit groups in the second part.
The dividing the plurality of columns into the first and second parts may be performed based on at least one of a number of the columns, a number of the bit groups constituting the LDPC codeword, and a number of bits constituting each of the bit groups.
If a number of bit groups constituting the LDPC codeword is an integer multiple of a number of the columns, the interleaving the plurality of bit groups may be performed by writing all bits included in the bit groups serially in the plurality of columns without the dividing the plurality of columns into the first and second parts.
According to various exemplary embodiments, improved decoding and receiving performance can be provided.
The above and/or other aspects will be more apparent by describing in detail exemplary embodiments, with reference to the accompanying drawings, in which:
Hereinafter, various exemplary embodiments will be described in greater detail with reference to the accompanying drawings.
In the following description, same reference numerals are used for the same elements when they are depicted in different drawings. The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the exemplary embodiments. Thus, it is apparent that the exemplary embodiments can be carried out without those specifically defined matters. Also, functions or elements known in the related art are not described in detail since they would obscure the exemplary embodiments with unnecessary detail.
According to
The transmitting apparatus 10000 according to an exemplary embodiment illustrated in
The Input Formatting block 11000, 110001 generates a baseband frame (BBFRAME) from an input stream of data to be serviced. Herein, the input stream may be a transport stream (TS), Internet protocol (IP) stream, a generic stream (GS), a generic stream encapsulation (GSE), etc.
The BICM block 12000, 120001 determines a forward error correction (FEC) coding rate and a constellation order depending on a region where the data to be serviced will be transmitted (e.g., a fixed PHY frame or mobile PHY frame), and then, performs encoding. Signaling information on the data to be serviced may be encoded through a separate BICM encoder (not illustrated) or encoded by sharing the BICM encoder 12000, 120001 with the data to be serviced, depending on a system implementation.
The Framing/Interleaving block 13000, 130001 combines time interleaved data with signaling information to generate a transmission frame.
The Waveform Generation block 14000, 140001 generates an OFDM signal in the time domain on the generated transmission frame, modulates the generated OFDM signal to a radio frequency (RF) signal and transmits the modulated RF signal to a receiver.
In the TDM system architecture, there are four main blocks (or parts): the Input Formatting block 11000, the BICM block 12000, the Framing/Interleaving block 13000, and the Waveform Generation block 14000.
Data is input and formatted in the Input Formatting block, and forward error correction applied and mapped to constellations in the BICM block 12000. Interleaving, both time and frequency, and frame creation done in the Framing/Interleaving block 13000. Subsequently, the output waveform is created in the Waveform Generation block 14000.
In the LDM system architecture, there are several different blocks compared with the TDM system architecture. Specifically, there are two separate Input Formatting blocks 11000, 110001 and BICM blocks 12000, 120001, one for each of the layers in LDM. These are combined before the Framing/Interleaving block 13000 in the LDM Injection block. The Waveform Generation block 14000 is similar to TDM.
As illustrated in
Input data packets input to the Input Formatting block 11000 can consist of various types, but at the encapsulation operation these different types of packets become generic packets which configure baseband frames. Here, the format of generic packets is variable. It is possible to easily extract the length of the generic packet from the packet itself without additional information. The maximum length of the generic packet is 64 kB. The maximum length of the generic packet, including header, is four bytes. Generic packets must be of integer byte length.
The scheduler 11200 receives an input stream of encapsulated generic packets and forms them into physical layer pipes (PLPs), in the form of baseband frames. In the abovementioned TDM system there may be only one PLP, called single PLP or SPLP, or there may be multiple PLPs, called MPLP. One service cannot use more than four PLPs. In the case of an LDM system consisting of two layers, two PLPs are used, one for each layer.
The scheduler 11200 receives encapsulated input packet streams and directs how these packets are allocated to physical layer resources. Specifically, the scheduler 11200 directs how the baseband framing block will output baseband frames.
The functional assets of the Scheduler 11200 are defined by data size(s) and time(s). The physical layer can deliver portions of data at these discrete times. The scheduler 11200 uses the inputs and information including encapsulated data packets, quality of service metadata for the encapsulated data packets, a system buffer model, constraints and configuration from system management, and creates a conforming solution in terms of configuration of the physical layer parameters. The corresponding solution is subject to the configuration and control parameters and the aggregate spectrum available.
Meanwhile, the operation of the Scheduler 11200 is constrained by combination of dynamic, quasistatic, and static configurations. The definition of these constraints is left to implementation.
In addition, for each service a maximum of four PLPs shall be used. Multiple services consisting of multiple time interleaving blocks may be constructed, up to a total maximum of 64 PLPs for bandwidths of 6, 7 or 8 MHz. The baseband framing block 11300, as illustrated in
A baseband frame 3500, as illustrated in
The baseband frame header construction block 3200, 32001, . . . 3200n configures the baseband frame header. The baseband frame header 35001, as illustrated in
The main feature of the base header 3710 is to provide a pointer including an offset value in bytes as an initiation of the next generic packet within the baseband frame. When the generic packet initiates the baseband frame, the pointer value becomes zero. If there is no generic packet which is initiated within the baseband frame, the pointer value is 8191, and a 2byte base header may be used.
The extension field (or extension header) 3730 may be used later, for example, for the baseband frame packet counter, baseband frame time stamping, and additional signaling, etc.
The baseband frame scrambling block 3300, 33001, . . . 3300n scrambles the baseband frame.
In order to ensure that the payload data when mapped to constellations does not always map to the same point, such as when the payload mapped to constellations consists of a repetitive sequence, the payload data shall always be scrambled before forward error correction encoding.
The scrambling sequences shall be generated by a 16bit shift register that has 9 feedback taps. Eight of the shift register outputs are selected as a fixed randomizing byte, where each bit from t his byte is used to individually XOR the corresponding input data. The data bits are XORed MSB to MSB and so on until LSB to LSB. The generator polynomial is G(x)=1+X+X^{3}+X^{6}+X^{7}+X^{11}+X^{12}+X^{13}+X^{16}.
As illustrated in
The input to the FEC block 1400, 141001, . . . , 14100n is a Baseband frame, of length K_{payload}, and the output from the FEC block is a FEC frame. The FEC block 14100, 141001, . . . , 14100n is implemented by concatenation of an outer code and an innter code with the information part. The FEC frame has length N_{inner}. There are two different lengths of LDPC code defined: N_{inner}=64800 bits and N_{inner}=16200 bits
The outer code is realized as one of either Bose, RayChaudhuri and Hocquenghem (BCH) outer code, a Cyclic Redundancy Check (CRC) or other code. The inner code is realized as a Low Density Parity Check (LDPC) code. Both BCH and LDPC FEC codes are systematic codes where the information part I contained within the codeword. The resulting codeword is thus a concatenation of information or payload part, BCH or CRC parities and LDPC parities, as shown in
The use of LDPC code is mandatory and is used to provide the redundancy needed for the code detection. There are two different LDPC structures that are defined, these are called Type A and Type B. Type A has a code structure that shows better performance at low code rates while Type B code structure shows better performance at high code rates. In general N_{inner}=64800 bit codes are expected to be employed. However, for applications where latency is critical, or a simpler encoder/decoder structure is preferred, N_{inner}=16200 bit codes may also be used.
The outer code and CRC consist of adding M_{outer }bits to the input baseband frame. The outer BCH code is used to lower the inherent LDPC error floor by correcting a predefined number of bit errors. When using BCH codes the length of M_{outer }is 192 bits (N_{inner}=64800 bit codes) and 168 bits (for N_{inner}=16200 bit codes). When using CRC the length of M_{outer }is 32 bits. When neither BCH nor CRC are used the length of M_{outer }is zero. The outer code may be omitted if it is determined that the error correcting capability of the inner code is sufficient for the application. When there is no outer code the structure of the FEC frame is as shown in
The LDPC codeword of the LDPC encoder, i.e., a FEC Frame, shall be bit interleaved by a Bit Interleaver block 14200. The Bit Interleaver block 14200 includes a parity interleaver 14210, a groupwise interleaver 14220 and a block interleaver 14230. Here, the parity interleaver is not used for Type A and is only used for Type B codes.
The parity interleaver 14210 converts the staircase structure of the paritypart of the LDPC paritycheck matrix into a quasicyclic structure similar to the informationpart of the matrix.
Meanwhile, the parity interleaved LDPC coded bits are split into N_{group}=N_{inner}/360 bit groups, and the groupwise interleaver 14220 rearranges the bit groups.
The block interleaver 14230 block interleaves the groupwise interleaved LDPC codeword.
Specifically, the block interleaver 14230 divides a plurality of columns into part 1 and part 2 based on the number of columns of the block interleaver 14230 and the number of bits of the bit groups. In addition, the block interleaver 14230 writes the bits into each column configuring part 1 column wise, and subsequently writes the bits into each column configuring part 2 column wise, and then reads out row wise the bits written in each column.
In this case, the bits constituting the bit groups in the part 1 may be written into the same column, and the bits constituting the bit groups in the part 2 may be written into at least two columns.
Back to
Each FEC frame shall be mapped to a FEC block by first demultiplexing the input bits into parallel data cell words and then mapping these cell words into constellation values.
As illustrated in
The input to the time interleaving block 14310 and the framing block 14320 may consist of MPLPs however the output of the framing block 14320 is OFDM symbols, which are arranged in frames. The frequency interleaver included in the frequency interleaving block 14330 operates an OFDM symbols.
The time interleaver (TI) configuration included in the time interleaving block 14310 depends on the number of PLPs used. When there is only a single PLP or when LDM is used, a sheer convolutional interleaver is used, while for multiple PLP a hybrid interleaver consisting of a cell interleaver, a block interleaver and a convolutional interleaver is used. The input to the time interleaving block 14310 is a stream of cells output from the mapper block (
The framing block 14320 maps the interleaved frames onto at least one transmitter frame. The framing block 14320, specifically, receives inputs (e.g. data cell) from at least one physical layer pipes and outputs symbols.
In addition, the framing block 14320 creates at least one special symbol known as preamble symbols. These symbols undergo the same processing in the waveform block mentioned later.
As illustrated in
Meanwhile, the purpose of the frequency interleaving block 14330 is to ensure that sustained interference in one part of the spectrum will not degrade the performance of a particular PLP disproportionately compared to other PLPs. The frequency interleaver 14330, operating on the all the data cells of one OFDM symbol, maps the data cells from the framing block 14320 onto the N data carriers.
As illustrated in
The pilot inserting block 14100 inserts a pilot to various cells within the OFDM frame.
Various cells within the OFDM frame are modulated with reference information whose transmitted value is known to the receiver.
Cells containing the reference information are transmitted at a boosted power level. The cells are called scattered, continual, edge, preamble or frameclosing pilot cells. The value of the pilot information is derived from a reference sequence, which is a series of values, one for each transmitted carrier on any given symbol.
The pilots can be used for frame synchronization, frequency synchronization, time synchronization, channel estimation, transmission mode identification and can also be used to follow the phase noise.
The pilots are modulated according to reference information, and the reference sequence is applied to all the pilots (e.g. scattered, continual edge, preamble and frame closing pilots) in every symbol including preamble and the frameclosing symbol of the frame.
The reference information, taken from the reference sequence, is transmitted in scattered pilot cells in every symbol except the preamble and the frameclosing symbol of the frame.
In addition to the scattered pilots described above, a number of continual pilots are inserted in every symbol of the frame except for Preamble and the frameclosing symbol. The number and location of continual pilots depends on both the FFT size and scattered pilot pattern in use.
The MISO block 14200 applies a MISO processing.
The Transmit Diversity Code Filter Set is a MISO predistortion technique that artificially decorrelates signals from multiple transmitters in a Single Frequency Network in order to minimize potential destructive interference. Linear frequency domain filters are used so that the compensation in the receiver can be implemented as part of the equalizer process. The filter design is based on creating allpass filters with minimized crosscorrelation over all filter pairs under the constraints of the number of transmitters Mε{2, 3, 4} and the time domain span of the filters Nε{64,256}. The longer time domain span filters will increase the decorrelation level, but the effective guard interval length will be decreased by the filter time domain span and this should be taken into consideration when choosing a filter set for a particular network topology.
The IFFT block 14300 specifies the OFDM structure to use for each transmission mode. The transmitted signal is organized in frames. Each frame has a duration of T_{F}, and consists of L_{F }OFDM symbols. N frames constitute one superframe. Each symbol is constituted by a set of K_{total }carriers transmitted with a duration T_{S}. Each symbol is composed of a useful part with duration T_{U }and a guard interval with a duration Δ. The guard interval consists of a cyclic continuation of the useful part, T_{U}, and is inserted before it.
The PAPR block 14400 applies the Peak to Average Power Reduction technique.
The GI inserting block 14500 inserts the guard interval into each frame.
The bootstrap block 14600 prefixes the bootstrap signal to the front of each frame.
The input processing block 11000 includes a scheduler 11200. The BICM block 15000 includes an L1 signaling generator 15100, an FEC encoder 152001 and 152002, a bit interleaver 153002, a demux 154002, constellation mappers 155001 and 155002. The L1 signaling generator 15100 may be included in the input processing block 11000, according to an exemplary embodiment.
An n number of service data are mapped to a PLPO to a PLPn respectively. The scheduler 11200 determines a position, modulation and coding rate for each PLP in order to map a plurality of PLPs to a physical layer of T2. In other words, the scheduler 11200 generates L1 signaling information. The scheduler 11200 may output dynamic field information among L1 post signaling information of a current frame, using the Framing/Interleavingblock 13000 (
The L1 signaling generator 15100 may differentiate the L1 pre signaling information from the L1 post signaling information to output them. The FEC encoders 152001 and 152002 perform respective encoding operations which include shortening and puncturing for the L1 pre signaling information and the L1 post signaling information. The bit interleaver 153002 performs interleaving by bit for the encoded L1 post signaling information. The demux 154002 controls robustness of bits by modifying an order of bits constituting cells and outputs the cells which include bits. Two constellation mappers 155001 and 155002 map the L1 pre signaling information and the L1 post signaling information to constellations, respectively. The L1 pre signaling information and the L1 post signaling information processed through the above described processes are output to be included in each frame by the Framing/Interleaving block 13000 (
The apparatus 20000 for receiving broadcast signals according to an embodiment of the present invention can correspond to the apparatus 10000 for transmitting broadcast signals, described with reference to
The synchronization & demodulation module 21000 can receive input signals through m Rx antennas, perform signal detection and synchronization with respect to a system corresponding to the apparatus 20000 for receiving broadcast signals and carry out demodulation corresponding to a reverse procedure of the procedure performed by the apparatus 10000 for transmitting broadcast signals.
The frame parsing module 22000 can parse input signal frames and extract data through which a service selected by a user is transmitted. If the apparatus 10000 for transmitting broadcast signals performs interleaving, the frame parsing module 22000 can carry out deinterleaving corresponding to a reverse procedure of interleaving. In this case, the positions of a signal and data that need to be extracted can be obtained by decoding data output from the signaling decoding module 25200 to restore scheduling information generated by the apparatus 10000 for transmitting broadcast signals.
The demapping & decoding module 23000 can convert the input signals into bit domain data and then deinterleave the same as necessary. The demapping & decoding module 23000 can perform demapping for mapping applied for transmission efficiency and correct an error generated on a transmission channel through decoding. In this case, the demapping & decoding module 23000 can obtain transmission parameters necessary for demapping and decoding by decoding the data output from the signaling decoding module 25000.
The output processor 24000 can perform reverse procedures of various compression/signal processing procedures which are applied by the apparatus 10000 for transmitting broadcast signals to improve transmission efficiency. In this case, the output processor 24000 can acquire necessary control information from data output from the signaling decoding module 25000. The output of the output processor 24000 corresponds to a signal input to the apparatus 10000 for transmitting broadcast signals and may be MPEGTSs, IP streams (v4 or v6) and generic streams.
The signaling decoding module 25000 can obtain PLS information from the signal demodulated by the synchronization & demodulation module 21000. As described above, the frame parsing module 22000, demapping & decoding module 23000 and output processor 24000 can execute functions thereof using the data output from the signaling decoding module 25000.
As shown in
The first processing block 21000 can include a tuner 21100, an ADC block 21200, a preamble detector 21300, a guard sequence detector 21400, a waveform transform block 21500, a time/frequency synchronization block 21600, a reference signal detector 21700, a channel equalizer 21800 and an inverse waveform transform block 21900.
The tuner 21100 can select a desired frequency band, compensate for the magnitude of a received signal and output the compensated signal to the ADC block 21200.
The ADC block 21200 can convert the signal output from the tuner 21100 into a digital signal.
The preamble detector 21300 can detect a preamble (or preamble signal or preamble symbol) in order to check whether or not the digital signal is a signal of the system corresponding to the apparatus 20000 for receiving broadcast signals. In this case, the preamble detector 21300 can decode basic transmission parameters received through the preamble.
The guard sequence detector 21400 can detect a guard sequence in the digital signal. The time/frequency synchronization block 21600 can perform time/frequency synchronization using the detected guard sequence and the channel equalizer 21800 can estimate a channel through a received/restored sequence using the detected guard sequence.
The waveform transform block 21500 can perform a reverse operation of inverse waveform transform when the apparatus 10000 for transmitting broadcast signals has performed inverse waveform transform. When the broadcast transmission/reception system according to one embodiment of the present invention is a multicarrier system, the waveform transform block 21500 can perform FFT. Furthermore, when the broadcast transmission/reception system according to an embodiment of the present invention is a single carrier system, the waveform transform block 21500 may not be used if a received time domain signal is processed in the frequency domain or processed in the time domain.
The time/frequency synchronization block 21600 can receive output data of the preamble detector 21300, guard sequence detector 21400 and reference signal detector 21700 and perform time synchronization and carrier frequency synchronization including guard sequence detection and block window positioning on a detected signal. Here, the time/frequency synchronization block 21600 can feed back the output signal of the waveform transform block 21500 for frequency synchronization.
The reference signal detector 21700 can detect a received reference signal. Accordingly, the apparatus 20000 for receiving broadcast signals according to an embodiment of the present invention can perform synchronization or channel estimation.
The channel equalizer 21800 can estimate a transmission channel from each Tx antenna to each Rx antenna from the guard sequence or reference signal and perform channel equalization for received data using the estimated channel.
The inverse waveform transform block 21900 may restore the original received data domain when the waveform transform block 21500 performs waveform transform for efficient synchronization and channel estimation/equalization. If the broadcast transmission/reception system according to an embodiment of the present invention is a single carrier system, the waveform transform block 21500 can perform FFT in order to carry out synchronization/channel estimation/equalization in the frequency domain and the inverse waveform transform block 21900 can perform IFFT on the channelequalized signal to restore transmitted data symbols. If the broadcast transmission/reception system according to an embodiment of the present invention is a multicarrier system, the inverse waveform transform block 21900 may not be used.
The abovedescribed blocks may be omitted or replaced by blocks having similar or identical functions according to design.
As shown in
The block interleaver 22100 can deinterleave data input through data paths of the m Rx antennas and processed by the synchronization & demodulation module 21000 on a signal block basis. In this case, if the apparatus 10000 for transmitting broadcast signals performs pairwise interleaving, the block interleaver 22100 can process two consecutive pieces of data as a pair for each input path. Accordingly, the block interleaver 22100 can output two consecutive pieces of data even when deinterleaving has been performed. Furthermore, the block interleaver 22100 can perform a reverse operation of the interleaving operation performed by the apparatus 10000 for transmitting broadcast signals to output data in the original order.
The cell demapper 22200 can extract cells corresponding to common data, cells corresponding to data pipes and cells corresponding to PLS data from received signal frames. The cell demapper 22200 can merge data distributed and transmitted and output the same as a stream as necessary. When two consecutive pieces of cell input data are processed as a pair and mapped in the apparatus 10000 for transmitting broadcast signals, the cell demapper 22200 can perform pairwise cell demapping for processing two consecutive input cells as one unit as a reverse procedure of the mapping operation of the apparatus 10000 for transmitting broadcast signals.
In addition, the cell demapper 22200 can extract PLS signaling data received through the current frame as PLSpre & PLSpost data and output the PLSpre & PLSpost data.
The abovedescribed blocks may be omitted or replaced by blocks having similar or identical functions according to design.
The demapping & decoding module 23000 shown in
The bit interleaved and coded & modulation module of the apparatus 10000 for transmitting broadcast signals according to an embodiment of the present invention can process input data pipes by independently applying SISO, MISO and MIMO thereto for respective paths, as described above. Accordingly, the demapping & decoding module 23000 illustrated in
As shown in
A description will be given of each block of the demapping & decoding module 23000.
The first block 23100 processes an input data pipe according to SISO and can include a time deinterleaver block 23110, a cell deinterleaver block 23120, a constellation demapper block 23130, a celltobit mux block 23140, a bit deinterleaver block 23150 and an FEC decoder block 23160.
The time deinterleaver block 23110 can perform a reverse process of the process performed by the time interleaving block 14310 illustrated in
The cell deinterleaver block 23120 can perform a reverse process of the process performed by the cell interleaver block illustrated in
The constellation demapper block 23130 can perform a reverse process of the process performed by the mapper 12300 illustrated in
The celltobit mux block 23140 can perform a reverse process of the process performed by the mapper 12300 illustrated in
The bit deinterleaver block 23150 can perform a reverse process of the process performed by the bit interleaver 12200 illustrated in
The FEC decoder block 23460 can perform a reverse process of the process performed by the FEC encoder 12100 illustrated in
The second block 23200 processes an input data pipe according to MISO and can include the time deinterleaver block, cell deinterleaver block, constellation demapper block, celltobit mux block, bit deinterleaver block and FEC decoder block in the same manner as the first block 23100, as shown in
The MISO decoding block 11110 can perform a reverse operation of the operation of the MISO processing in the apparatus 10000 for transmitting broadcast signals. If the broadcast transmission/reception system according to an embodiment of the present invention uses STBC, the MISO decoding block 11110 can perform Alamouti decoding.
The third block 23300 processes an input data pipe according to MIMO and can include the time deinterleaver block, cell deinterleaver block, constellation demapper block, celltobit mux block, bit deinterleaver block and FEC decoder block in the same manner as the second block 23200, as shown in
The MIMO decoding block 23310 can receive output data of the cell deinterleaver for input signals of the m Rx antennas and perform MIMO decoding as a reverse operation of the operation of the MIMO processing in the apparatus 10000 for transmitting broadcast signals. The MIMO decoding block 23310 can perform maximum likelihood decoding to obtain optimal decoding performance or carry out sphere decoding with reduced complexity. Otherwise, the MIMO decoding block 23310 can achieve improved decoding performance by performing MMSE detection or carrying out iterative decoding with MMSE detection.
The fourth block 23400 processes the PLSpre/PLSpost information and can perform SISO or MISO decoding.
The basic roles of the time deinterleaver block, cell deinterleaver block, constellation demapper block, celltobit mux block and bit deinterleaver block included in the fourth block 23400 are identical to those of the corresponding blocks of the first, second and third blocks 23100, 23200 and 23300 although functions thereof may be different from the first, second and third blocks 23100, 23200 and 23300.
The shortened/punctured FEC decoder 23410 can perform deshortening and depuncturing on data shortened/punctured according to PLS data length and then carry out FEC decoding thereon. In this case, the FEC decoder used for data pipes can also be used for PLS. Accordingly, additional FEC decoder hardware for the PLS only is not needed and thus system design is simplified and efficient coding is achieved.
The abovedescribed blocks may be omitted or replaced by blocks having similar or identical functions according to design.
The demapping & decoding module according to an embodiment of the present invention can output data pipes and PLS information processed for the respective paths to the output processor, as illustrated in
The output processor 24000 shown in
The BB scrambler block 24100 can descramble an input bit stream by generating the same PRBS as that used in the apparatus for transmitting broadcast signals for the input bit stream and carrying out an XOR operation on the PRBS and the bit stream.
The padding removal block 24200 can remove padding bits inserted by the apparatus for transmitting broadcast signals as necessary.
The CRC8 decoder block 24300 can check a block error by performing CRC decoding on the bit stream received from the padding removal block 24200.
The BB frame processor block 24400 can decode information transmitted through a BB frame header and restore MPEGTSs, IP streams (v4 or v6) or generic streams using the decoded information.
The abovedescribed blocks may be omitted or replaced by blocks having similar or identical functions according to design.
The output processor 24000 shown in
A dejitter buffer block 24500 included in the output processor shown in
A null packet insertion block 24600 can restore a null packet removed from a stream with reference to a restored DNP (deleted null packet) and output common data.
A TS clock regeneration block 24700 can restore time synchronization of output packets based on ISCR (input stream time reference) information.
A TS recombining block 24800 can recombine the common data and data pipes related thereto, output from the null packet insertion block 24600, to restore the original MPEGTSs, IP streams (v4 or v6) or generic streams. The TTO, DNT and ISCR information can be obtained through the BB frame header.
An inband signaling decoding block 24900 can decode and output inband physical layer signaling information transmitted through a padding bit field in each FEC frame of a data pipe.
The output processor shown in
The abovedescribed blocks may be omitted or replaced by blocks having similar r identical functions according to design.
The encoder 110 generates a low density parity check (LDPC) codeword by performing LDPC encoding based on a parity check matrix. The encoder 110 may include an LDPC encoder (not shown) to perform the LDPC encoding.
The encoder 110 LDPCencodes information word (or information) bits to generate the LDPC codeword which is formed of information word bits and parity bits (that is, LDPC parity bits). Here, bits input to the encoder 110 may be used as the information word bits. Also, since an LDPC code is a systematic code, the information word bits may be included in the LDPC codeword as they are.
The LDPC codeword is formed of the information word bits and the parity bits. For example, the LDPC codeword is formed of N_{ldpc }number of bits, and includes K_{ldpc }number of information word bits and N_{parity}=N_{ldpc}−K_{ldpc }number of parity bits.
In this case, the encoder 110 may generate the LDPC codeword by performing the LDPC encoding based on the parity check matrix. That is, since the LDPC encoding is a process for generating an LDPC codeword to satisfy H·C^{T}=0, the encoder 110 may use the parity check matrix when performing the LDPC encoding. Herein, H is a parity check matrix and C is an LDPC codeword.
For the LDPC encoding, the transmitting apparatus 100 may include a memory and may prestore parity check matrices of various formats.
For example, the transmitting apparatus 100 may prestore parity check matrices which are defined in Digital Video BroadcastingCable version 2 (DVBC2), Digital Video BroadcastingSatelliteSecond Generation (DVBS2), Digital Video BroadcastingSecond Generation Terrestrial (DVBT2), etc., or may prestore parity check matrices which are defined in the North America digital broadcasting standard system Advanced Television System Committee (ATSC) 3.0 standards, which are currently being established. However, this is merely an example and the transmitting apparatus 100 may prestore parity check matrices of other formats in addition to these parity check matrices.
Hereinafter, a parity check matrix according to various exemplary embodiments will be explained with reference to the drawings. In the parity check matrix, elements other than elements having 1 have 0.
For example, the parity check matrix according to an exemplary embodiment may have a configuration of
Referring to
The information word submatrix 210 includes K_{ldpc }number of columns and the parity submatrix 220 includes N_{panty}=N_{ldpc}−K_{ldpc }number of columns. The number of rows of the parity check matrix 200 is identical to the number of columns of the parity submatrix 220, N_{parity}=N_{ldpc}−K_{ldpc}.
In addition, in the parity check matrix 200, N_{ldpc }is a length of an LDPC codeword, K_{ldpc }is a length of information word bits, and N_{parity}=N_{ldpc}−K_{ldpc }is a length of parity bits. The length of the LDPC codeword, the information word bits, and the parity bits mean the number of bits included in each of the LDPC codeword, the information word bits, and the parity bits.
Hereinafter, the configuration of the information word submatrix 210 and the parity submatrix 220 will be explained.
The information word submatrix 210 includes K_{ldpc }number of columns (that is, 0^{th }column to (K_{ldpc}−1)^{th }column), and follows the following rules:
First, M number of columns from among K_{ldpc }number of columns of the information word submatrix 210 belong to the same group, and K_{ldpc }number of columns is divided into K_{ldpc}/M number of column groups. In each column group, a column is cyclicshifted from an immediately previous column by Q_{ldpc}. That is, Q_{ldpc }may be a cyclic shift parameter value regarding columns in a column group of the information word submatrix 210 of the parity check matrix 200.
Herein, M is an interval at which a pattern of a column group, which includes a plurality of columns, is repeated in the information word submatrix 210 (e.g., M=360), and Q_{ldpc }is a size by which one column is cyclicshifted from an immediately previous column in a same column group in the information word submatrix 210. Also, M is a common divisor of N_{ldpc }and K_{ldpc }and is determined to satisfy Q_{ldpc}=(N_{ldpc}−K_{ldpc})/M. Here, M and Q_{ldpc }are integers and K_{ldpc}/M is also an integer. M and Q_{ldpc }may have various values according to a length of the LDPC codeword and a code rate or coding rate (CR).
For example, when M=360 and the length of the LDPC codeword, N_{ldpc}, is 64800, Q_{ldpc }may be defined as in Table 1 presented below, and, when M=360 and the length N_{ldpc }of the LDPC codeword is 16200, Q_{ldpc }may be defined as in Table 2 presented below.
Second, when the degree of the 0^{th }column of the i^{th }column group (1=0, 1, . . . , K_{ldpc}/M−1) is D_{i }(herein, the degree is the number of value 1 existing in each column and all columns belonging to the same column group have the same degree), and a position (or an index) of each row where 1 exists in the 0^{th }column of the i^{th }column group is R_{i,0} ^{(0)}, R_{i,0} ^{(1)}, . . . , R_{i,0} ^{(D} ^{ i } ^{=1)}, an index R_{i,j} ^{(k) }of a row where k^{th }1 is located in the j^{th }column in the i^{th }column group is determined by following Equation 1:
R _{i,j} ^{(k)} =R _{i,(j−1)} ^{(k)} +Q _{ldpc }mod(N _{ldpc} −K _{ldpc}) (1),
where k=0, 1, 2, . . . D_{i}−1; i=0, 1, . . . , K_{ldpc}/M−1; and j=1, 2, . . . , M−1.
Equation 1 can be expressed as following Equation 2:
R _{i,j} ^{(k)} ={R _{i,0} ^{(k)}+(j mod M)×Q _{ldpc}} mod(N _{ldpc} −K _{ldpc}) (2),
where k=0, 1, 2, . . . D_{i}−1; i=0, 1, . . . , K_{ldpc}/M−1; and j=1, 2, . . . , M−1. Since j=1, 2, . . . , M−1, (j mod M) of Equation 2 may be regarded as j.
In the above equations, R_{i,j} ^{(k) }is an index of a row where k^{th }1 is located in the j^{th }column in the i^{th }column group, N_{ldpc }is a length of an LDPC codeword, K_{ldpc }is a length of information word bits, D_{i }is a degree of columns belonging to the i^{th }column group, M is the number of columns belonging to a single column group, and Q_{ldpc}, is a size by which each column in the column group is cyclicshifted.
As a result, referring to these equations, when only R_{i,0} ^{(k) }is known, the index R_{i,j} ^{(k) }of the row where the k^{th }1 is located in the j^{th }column in the i^{th }column group can be known. Therefore, when the index value of the row where the k^{th }1 is located in the 0^{th }column of each column group is stored, a position of column and row where 1 is located in the parity check matrix 200 having the configuration of
According to the abovedescribed rules, all of the columns belonging to the i^{th }column group have the same degree D_{i}. Accordingly, the LDPC codeword which stores information on the parity check matrix according to the abovedescribed rules may be briefly expressed as follows.
For example, when N_{ldpc }is 30, K_{ldpc }is 15, and Q_{ldpc }is 3, position information of the row where 1 is located in the 0^{th }column of the three column groups may be expressed by a sequence of Equations 3 and may be referred to as “weight1 position sequence”.
R _{1,0} ^{(1)}=1,R _{1,0} ^{(2)}=2,R _{1,0} ^{(3)}=8R _{1,0} ^{(4)}=10,
R _{2,0} ^{(1)}=0,R _{2,0} ^{(2)}=9,R _{2,0} ^{(3)}=13,
R _{3,0} ^{(1)}=0,R _{3,0} ^{(2)}=14. (3),
where R_{i,j} ^{(k) }is an index of a row where k^{th }1 is located in the j^{th }column in the i^{th }column group.
The weight1 position sequence like Equation 3 which expresses an index of a row where 1 is located in the 0^{th }column of each column group may be briefly expressed as in Table 3 presented below:
Table 3 shows positions of elements having value 1 in the parity check matrix, and the i^{th }weight1 position sequence is expressed by indexes of rows where 1 is located in the 0^{th }column belonging to the i^{th }column group.
The information word submatrix 210 of the parity check matrix according to an exemplary embodiment may be defined as in Tables 4 to 12 presented below, based on the above descriptions.
Tables 4 to 12 show indexes of rows where 1 is located in the 0^{th }column of the i^{th }column group of the information word submatrix 210. That is, the information word submatrix 210 is formed of a plurality of column groups each including M number of columns, and positions of 1 in the 0^{th }column of each of the plurality of column groups may be defined by Tables 4 to 12.
Herein, the indexes of the rows where 1 is located in the 0^{th }column of the i^{th }column group mean “addresses of parity bit accumulators”. The “addresses of parity bit accumulators” have the same meaning as defined in the DVBC2/S2/T2 standards or the ATSC 3.0 standards which are currently being established, and thus, a detailed explanation thereof is omitted.
For example, when the length N_{ldpc }of the LDPC codeword is 16200, the code rate is 5/15, and M is 360, the indexes of the rows where 1 is located in the 0^{th }column of the i^{th }column group of the information word submatrix 210 are as shown in Table 4 presented below:
In another example, when the length N_{ldpc }of the LDPC codeword is 16200, the code rate is 7/15, and M is 360, the indexes of the rows where 1 is located in the 0^{th }column of the i^{th }column group of the information word submatrix 210 are as shown in Table 5 or Table 6 presented below:
In another example, when the length N_{ldpc }of the LDPC codeword is 16200, the code rate is 9/15, and M is 360, the indexes of rows where 1 exists in the 0^{th }column of the i^{th }column group of the information word submatrix 210 are defined as shown in Table 7 or Table 8 below.
In another example, when the length N_{ldpc }of the LDPC codeword is 16200, the code rate is 11/15, and M is 360, the indexes of rows where 1 exists in the 0^{th }column of the i^{th }column group of the information word submatrix 210 are defined as shown in Table 9 or Table 10 below.
In another example, when the length N_{ldpc }of the LDPC codeword is 16200, the code rate is 13/15, and M is 360, the indexes of rows where 1 exists in the 0^{th }column of the i^{th }column group of the information word submatrix 210 are defined as shown in Table 11 or 12 below.
In the abovedescribed examples, the length of the LDPC codeword is 16200 and the code rate is 5/15, 7/15, 9/15, 11/15 and 13/15. However, this is merely an example, and the position of 1 in the information word submatrix 210 may be defined variously when the length of the LDPC codeword is 64800 or the code rate has different values.
According to an exemplary embodiment, even when an order of indexes in a sequence in the 0^{th }column of each column group of the parity check matrix 200 as shown in the abovedescribed Tables 4 to 12 is changed, the changed parity check matrix is a parity check matrix used for the same code. Therefore, a case in which the order of indexes in the sequence in the 0^{th }column of each column group in Tables 4 to 12 is changed is covered by the inventive concept.
According to an exemplary embodiment, even when the arrangement order of sequences corresponding the i+1 number of column groups is changed in Tables 4 to 12, cycle characteristics on a graph of a code and algebraic characteristics such as degree distribution are not changed. Therefore, a case in which the arrangement order of the sequences shown in Tables 4 to 12 is changed is also covered by the inventive concept.
In addition, even when a multiple of Q_{ldpc }is equally added to all indexes in a certain column group (i.e., a sequence) in Tables 4 to 12, the cycle characteristics on the graph of the code or the algebraic characteristics such as degree distribution are not changed. Therefore, a result of equally adding a multiple of Q_{ldpc }to all indexes shown in Tables 4 to 12 is also covered by the inventive concept. However, it should be noted that, when the resulting value obtained by adding the multiple of Q_{ldpc }to all indexes in a given sequence is greater than or equal to (N_{ldpc}−K_{ldpc}), a value obtained by applying a modulo operation to (N_{ldpc}−K_{ldpc}) should be applied instead.
Once positions of the rows where 1 exists in the 0^{th }column of the i^{th }column group of the information word submatrix 210 are defined as shown in Tables 4 to 12, positions of rows where 1 exists in other columns of each column group may be defined since the positions of the rows where 1 exists in the 0^{th }column are cyclicshifted by Q_{ldpc }in the next column.
For example, in the case of Table 4, in the 0^{th }column of the 0^{th }column group of the information word submatrix 210, 1 exists in the 245^{th }row, 449^{nd }row, 4911^{st }row, . . . .
In this case, since Q_{ldpc}=(N_{ldpc}−K_{ldpc})/M=(16200−5400)/360=30, the indexes of the rows where 1 is located in the 1^{st }column of the 0^{th }column group may be 275 (=245+30), 479 (=449+30), 521 (=491+30), . . . , and the indexes of the rows where 1 is located in the 2^{nd }column of the 0^{th }column group may be 305 (=275+30), 509 (=479+30), 551 (=521+30), . . . .
In the abovedescribed method, the indexes of the rows where 1 is located in all rows of each column group may be defined.
The parity submatrix 220 of the parity check matrix 200 shown in
The parity submatrix 220 includes N_{ldpc}−K_{ldpc }number of columns (that is, K_{ldpc} ^{th }column to (N_{ldpc}−1)^{th }column), and has a dual diagonal or staircase configuration. Accordingly, the degree of columns except the last column (that is, (N_{ldpc}−1)^{th }column) from among the columns included in the parity submatrix 220 is 2, and the degree of the last column is 1.
As a result, the information word submatrix 210 of the parity check matrix 200 may be defined by Tables 4 to 12, and the parity submatrix 220 of the parity check matrix 200 may have a dual diagonal configuration.
When the columns and rows of the parity check matrix 200 shown in
Q _{ldpc} ·i+j
K _{ldpc} +Q _{ldpc} ·k+l K _{ldpc} +M·l+k(0≦k<M,0≦l<Q _{ldpc}) (5)
The method for permutation based on Equation 4 and Equation 5 will be explained below. Since row permutation and column permutation apply the same principle, the row permutation will be explained as an example.
In the case of the row permutation, regarding the X^{th }row, i and j satisfying X=Q_{ldpc}×i+j are calculated and the X^{th }row is permutated by assigning the calculated i and j to M×j+i. For example of Q_{ldpc }and M being 2 and 10, respectively, regarding the 7^{th }row, i and j satisfying 7=2×i+j are 3 and 1, respectively. Therefore, the 7^{th }row is permutated to the 13^{th }row (10×1+3=13).
When the row permutation and the column permutation are performed in the abovedescribed method, the parity check matrix of
Referring to
Accordingly, the parity check matrix 300 having the configuration of
Since the parity check matrix 300 is formed of the quasicyclic matrices of M×M, M number of columns may be referred to as a column block and M number of rows may be referred to as a row block. Accordingly, the parity check matrix 300 having the configuration of
Hereinafter, the submatrix of M×M will be explained.
First, the (N_{qc} _{_} _{column}−1)^{th }column block of the 0^{th }row block has a form shown in Equation 6 presented below:
As described above, A 330 is an M×M matrix, values of the 0^{th }row and the (M−1)^{th }column are all “0”, and, regarding 0≦i≦(M−2), the (i+1)^{th }row of the i^{th }column is “1” and the other values are “0”.
Second, regarding 0≦i≦(N_{ldpc}−K_{ldpc})/M−1 in the parity submatrix 320, the i^{th }row block of the (K_{ldpc}/M+i)^{th }column block is configured by a unit matrix I_{M×M } 340. In addition, regarding 0≦i≦(N_{ldpc}−K_{ldpc})/M−2, the (i+1)^{th }row block of the (K_{ldpc}/M+i)^{th }column block is configured by a unit matrix I_{M×M } 340.
Third, a block 350 constituting the information word submatrix 310 may have a cyclicshifted format of a cyclic matrix P, P^{a} ^{ ij }, or an added format of the cyclicshifted matrix P^{a} ^{ ij }of the cyclic matrix P (or an overlapping format).
For example, a format in which the cyclic matrix P is cyclicshifted to the right by 1 may be expressed by Equation 7 presented below:
The cyclic matrix P is a square matrix having an M×M size and is a matrix in which a weight of each of M number of rows is 1 and a weight of each of M number of columns is 1. When a_{ij }is 0, the cyclic matrix P, that is, P^{0 }indicates a unit matrix I_{M×M}, and when a_{ij }is ∞, P^{∞} is a zero matrix.
A submatrix existing where the i^{th }row block and the j^{th }column block intersect in the parity check matrix 300 of
Hereinafter, a method for performing LDPC encoding based on the parity check matrix 200 as shown in
First, when information word bits having a length of K_{ldpc }are [i_{0}, i_{1}, i_{2}, . . . , i_{K} _{ ldpc } _{−1}], and parity bits having a length of N_{ldpc}−K_{ldpc }are [p_{0}, p_{1}, p_{2}, . . . p_{N} _{ ldpc } _{−K} _{ ldpc } _{−1}], the LDPC encoding is performed by the following process.
Step 1) Parity bits are initialized as ‘0’. That is, p_{0}=p_{1}=p_{2}= . . . =p_{N} _{ ldpc } _{−K} _{ ldpc } _{−1}=0.
Step 2) The 0^{th }information word bit i_{0 }is accumulated in parity bits having the indexes defined in the first row (that is, the row of i=0) of Table 4 as addresses of the parity bits. This may be expressed by Equation 8 presented below:
Here, i_{0 }is a 0^{th }information word bit, p_{i }is an i^{th }parity bit, and ⊕ is a binary operation. According to the binary operation, 10⊕1 equals 0, 10⊕0 equals 1, 0⊕1 equals 1, 0⊕0 equals 0.
Step 3) The other 359 information word bits i_{m }(m=1, 2, . . . , 359) are accumulated in parity bits having addresses calculated based on Equation 9 below. These information word bits may belong to the same column group as that of i_{0}.
(x+(m mod 360)×Q _{ldpc})mod(N _{ldpc} −K _{ldpc}) (9)
Here, x is an address of a parity bit accumulator corresponding to the information word bit i_{0}, and Q_{ldpc }is a size by which each column is cyclicshifted in the information word submatrix, and may be 30 in the case of Table 4. In addition, since m=1, 2, . . . , 359, (m mod 360) in Equation 9 may be regarded as m.
As a result, the information word bits i_{m }(m=1,2, . . . , 359) are accumulated in parity bits having the addresses calculated based on Equation 9. For example, an operation as shown in Equation 10 presented below may be performed for the information word bit i_{1}:
Herein, i_{1 }is a 1^{st }information word bit, p_{i }is an i^{th }parity bit, and ⊕ is a binary operation. According to the binary operation, 10⊕1 equals 0, 10⊕0 equals 1, 0⊕1 equals 1, 0⊕0 equals 0.
Step 4) The 360^{th }information word bits i_{360 }is accumulated in parity bits having indexes defined in the 2^{nd }row (that is, the row of i=1) of Table 4 as addresses of the parity bits.
Step 5) The other 359 information word bits belonging to the same group as that of the information word bit i_{360 }are accumulated in parity bits. In this case, an address of a parity bit may be determined based on Equation 9. However, in this case, x is an address of the parity bit accumulator corresponding to the information word bit i_{360}.
Step 6) Steps 4 and 5 described above are repeated for all of the column groups of Table 4.
Step 7) As a result, a parity bit p_{i }is calculated based on Equation 11 presented below. In this case, i is initialized as 1.
p _{i} =p _{i} ⊕p _{i−1} i=1,2, . . . ,N _{ldpc} −K _{ldpc}−1 (11)
In Equation 11, p_{i }is an i^{th }parity bit, N_{ldpc }is a length of an LDPC codeword, K_{ldpc }is a length of an information word of the LDPC codeword, and ⊕ is a binary operation.
The encoder 110 may calculate parity bits according to the abovedescribed method.
A parity check matrix may have a configuration as shown in
Referring to
First, M_{1}, M_{2}, Q_{1 }and Q_{2}, which are parameter values related to the parity check matrix 400 as shown in
The matrix A is formed of K number of columns and g number of rows, and the matrix C is formed of K+g number of columns and NKg number of rows. Here, K is a length of information word bits, and N is a length of the LDPC codeword.
Indexes of rows where 1 is located in the 0^{th }column of the i^{th }column group in the matrix A and the matrix C may be defined based on Table 14 according to the length and the code rate of the LDPC codeword. In this case, an interval at which a pattern of a column is repeated in each of the matrix A and the matrix C, that is, the number of columns belonging to a same group, may be 360.
For example, when the length N of the LDPC codeword is 16200 and the code rate is 5/15, the indexes of rows where 1 is located in the 0^{th }column of the i^{th }column group in the matrix A and the matrix C are defined as shown in Table 14 presented below:
In the abovedescribed example, the length of the LDPC codeword is 16200 and the code rate 5/15. However, this is merely an example and the indexes of rows where 1 is located in the 0^{th }column of the i^{th }column group in the matrix A and the matrix C may be defined differently when the length of the LDPC codeword is 64800 or the code rate has different values.
Hereinafter, positions of rows where 1 exists in the matrix A and the matrix C will be explained with reference to Table 14 by way of an example.
Since the length N of the LDPC codeword is 16200 and the code rate is 5/15 in Table 14, M_{1}=720, M_{2}=10080, Q_{1}=2, and Q_{2}=28 in the parity check matrix 400 defined by Table 14 with reference to Table 13.
Herein, Q_{1 }is a size by which columns of a same column group are cyclicshifted in the matrix A, and Q_{2 }is a size by which columns of a same column group are cyclicshifted in the matrix C.
In addition, Q_{1}=M_{1}/L, Q_{2}=M_{2}/L, M_{1}=g, and M_{2}=N−K−g, and L is an interval at which a pattern of a column is repeated in the matrix A and the matrix C, and for example, may be 360.
The index of a row where 1 is located in the matrix A and the matrix C may be determined based on the M_{1 }value.
For example, since M_{1}=720 in the case of Table 14, the positions of the rows where 1 exists in the 0^{th }column of the i^{th }column group in the matrix A may be determined based on values smaller than 720 from among the index values of Table 14, and the positions of the rows where 1 exists in the 0^{th }column of the i^{th }column group in the matrix C may be determined based on values greater than or equal to 720 from among the index values of Table 14.
In Table 14, the sequence corresponding to the 0^{th }column group is “69, 244, 706, 5145, 5994, 6066, 6763, 6815, and 8509”. Accordingly, in the case of the 0^{th }column of the 0^{th }column group of the matrix A, 1 may be located in the 69^{th }row, 244^{th }row, and 706^{th }row, and, in the case of the 0^{th }column of the 0^{th }column group of the matrix C, 1 may be located in the 5145^{th }row, 5994^{th }row, 6066^{th }row, 6763^{rd }row, 6815^{th }row, and 8509^{th }row.
Once positions of 1 in the 0^{th }column of each column group of the matrix A are defined, positions of rows where 1 exists in another column of the column group may be defined by cyclicshifting from an immediately previous column by Q_{1}. Once positions of 1 in the 0^{th }column of each column group of the matrix C are defined, position of rows where 1 exists in another column of the column group may be defined by cyclicshifting from the previous column by Q_{2}.
In the abovedescribed example, in the case of the 0^{th }column of the 0^{th }column group of the matrix A, 1 exists in the 69^{th }row, 244^{th }row, and 706^{th }row. In this case, since Q_{1}=2, the indexes of rows where 1 exists in the 1^{st }column of the 0^{th }column group are 71 (=69+2), 246 (=244+2), and 708 (=706+2), and the index of rows where 1 exists in the 2^{nd }column of the 0^{th }column group are 73 (=71+2), 248 (=246+2), and 710 (=708+2).
In the case of the 0^{th }column of the 0^{th }column group of the matrix C, 1 exists in the 5145^{th }row, 5994^{th }row, 6066^{th }row, 6763^{rd }row, 6815^{th }row, and 8509^{th }row. In this case, since Q_{2}=28, the index of rows where 1 exists in the 1^{st }column of the 0^{th }column group are 5173 (=5145+28), 6022 (=5994+28), 6094 (6066+28), 6791 (=6763+28), 6843 (=6815+28), and 8537 (=8509+28) and the indexes of rows where 1 exists in the 2^{nd }column of the 0^{th }column group are 5201 (=5173+28), 6050 (=6022+28), 6122 (=6094+28), 6819 (=6791+28), 6871 (=6843+28), and 8565 (=8537+28).
In this method, the positions of rows where 1 exists in all column groups of the matrix A and the matrix C are defined.
The matrix B may have a dual diagonal configuration, the matrix D may have a diagonal configuration (that is, the matrix D is an identity matrix), and the matrix Z may be a zero matrix.
As a result, the parity check matrix 400 shown in
Hereinafter, a method for performing LDPC encoding based on the parity check matrix 400 shown in
For example, when an information word block S=(s_{0}, s_{1}, . . . , S_{K−1}) is LDPCencoded, an LDPC codeword Λ=(λ_{0}, λ_{1}, . . . , λ_{N−1})=(s_{0}, s_{1}, . . . , S_{K−1}, p_{0}, p_{1}, . . . , P_{M} _{ 1 } _{+M} _{ 2 } _{−1}) including a parity bit P=(p_{0}, p_{1}, . . . , P_{M} _{ 1 } _{+M} _{ 2 } _{−1}) may be generated.
M_{1 }and M_{2 }indicate the size of the matrix B having the dual diagonal configuration and the size of the matrix D having the diagonal configuration, respectively, and M_{1}=g, M_{2}=N−K−g.
A process of calculating a parity bit is as follows. In the following explanation, the parity check matrix 400 is defined as shown in Table 14 as an example for the convenience of explanation.
Step 1) λ and p are initialized as λ_{i}=s_{i }(i=0, 1, . . . , K—1), p_{j}=0 (j=0, 1, . . . , M_{1}+M_{2}−1).
Step 2) The 0^{th }information word bit λ_{0 }is accumulated in parity bits having the indexes defined in the first row (that is, the row of i=0) of Table 14 as addresses of the parity bits. This may be expressed by Equation 12 presented below:
Step 3) Regarding the next L−1 number of information word bits (m=1, 2, . . . , L−1), λ_{m }is accumulated in parity bits address calculated based on Equation 13 presented below:
(χ+m×Q _{1})mod M _{1 }(if χ<M _{1})
M _{1}+{(χ−M _{1} +m×Q _{2})mod M _{2}}(if χ≧M _{1}) (13)
Here, x is an address of a parity bit accumulator corresponding to the 0^{th }information word bit λ_{0}.
In addition, Q_{1}=M_{1}/L and Q_{2}=M_{2}/L. In addition, since the length N of the LDPC codeword is 16200 and the code rate is 5/15 in Table 14, M_{1}=720, M_{2}=10080, Q_{1}=2, Q_{2}=28, and L=360 with reference to Table 13.
Accordingly, an operation as shown in Equation 14 presented below may be performed for the 1^{st }information word bit λ_{1};
Step 4) Since the same addresses of parity bits as in the second row (that is the row of i=1) of Table 14 are given with respect to the L^{th }information word bit λ_{L}, in a similar method to the abovedescribed method, addresses of parity bits regarding the next L−1 number of information word bits λ_{m }(m=L+1, L+2, . . . , 2L−1) are calculated based on Equation 13. In this case, x is an address of a parity bit accumulator corresponding to the information word bit λ_{L}, and may be obtained based on the second row of Table 14.
Step 5) The abovedescribed processes are repeated for L number of new information word bits of each bit group by considering new rows of Table 14 as addresses of the parity bit accumulator.
Step 6) After the abovedescribed processes are repeated for the codeword bits λ_{0 }to λ_{K−1}, values regarding Equation 15 presented below are calculated in sequence from i=1:
P _{i} =P _{i} ⊕P _{i−1}(i=1,2, . . . ,M _{1}−1) (15)
Step 7) Parity bits λ_{K }to λ_{K+M} _{ 1 } _{−1 }corresponding to the matrix B having the dual diagonal configuration are calculated based on Equation 16 presented below:
λ_{K+L×t+s} =p _{Q} _{ 1 } _{×S+t}(0≦s<L,0≦t>Q _{1}) (16)
Step 8) Addresses of a parity bit accumulator regarding L number of new codeword bits λ_{K }to λ_{K+M} _{ 1 } _{−1 }of each group are calculated based on Table 14 and Equation 13.
Step 9) After the codeword bits λ_{K }to λ_{K+M} _{ 1 } _{−1 }are calculated, parity bits λ_{K+M} _{ 1 }to λ_{K+M} _{ 1 } _{+M} _{ 2 } _{−1 }corresponding to the matrix C having the diagonal configuration are calculated based on Equation 17 presented below:
λ_{K+M} _{ 1 } _{+L×t+s} =p _{M} _{ 1 } _{+Q} _{ 2 } _{×S+t}(0≦s<L,0t≦Q _{2}) (17)
The encoder 110 may calculate parity bits according to the abovedescribed method.
Referring back to
In this case, the encoder 110 may perform the LDPC encoding by using a parity check matrix, and the parity check matrix is configured as shown in
In addition, the encoder 110 may perform Bose, Chaudhuri, Hocquenghem (BCH) encoding as well as LDPC encoding. To achieve this, the encoder 110 may further include a BCH encoder (not shown) to perform BCH encoding.
In this case, the encoder 110 may perform encoding in an order of BCH encoding and LDPC encoding. The encoder 110 may add BCH parity bits to input bits by performing BCH encoding and LDPCencodes the information word bits including the input bits and the BCH parity bits, thereby generating an LDPC codeword.
The interleaver 120 interleaves the LDPC codeword. That is, the interleaver 120 receives the LDPC codeword from the encoder 110, and interleaves the LDPC codeword based on various interleaving rules.
In particular, the interleaver 120 may interleave the LDPC codeword such that a bit included in a predetermined bit group from among a plurality of bit groups constituting the LDPC codeword (that is, a plurality of groups or a plurality of blocks) is mapped onto a predetermined bit of a modulation symbol. Accordingly, the modulator 130 may map a bit included in a predetermined group from among the plurality of groups of the LDPC codeword onto a predetermined bit of a modulation symbol.
To achieve this, as shown in
The parity interleaver 121 interleaves the parity bits constituting the LDPC codeword.
When the LDPC codeword is generated based on the parity check matrix 200 having the configuration of
u _{i} =c _{i }for 0≦i≦K _{ldpc}, and
u _{K} _{ ldpc } _{+M·t+s} =c _{K} _{ ldpc } _{+Q} _{ ldpc } _{·s+t }for 0≦s<M,0≦t<Q _{ldpc} (18),
where M is an interval at which a pattern of a column group is repeated in the information word submatrix 210, that is, the number of columns included in a column group (for example, M=360), and Q_{ldpc }is a size by which each column is cyclicshifted in the information word submatrix 210. That is, the parity interleaver 121 performs parity interleaving with respect to the LDPC codeword c=(c_{0}, c_{1}, . . . , c_{N} _{ ldpc } _{−1}), and outputs U=(u_{0}, u_{1}, . . . , u_{N} _{ ldpc } _{−1}).
The LDPC codeword of which parities are interleaved in the abovedescribed method may be configured such that a predetermined number of continuous bits of the LDPC codeword have similar decoding characteristics (cycle characteristics or cycle distribution, a degree of a column, etc.).
For example, the LDPC codeword may have same characteristics on the basis of M number of continuous bits. Here, M is an interval at which a pattern of a column group is repeated in the information word submatrix 210 and, for example, may be 360.
A product of the LDPC codeword bits and the parity check matrix should be “0”. This means that a sum of products of the i^{th }LDPC codeword bit, c_{i }(i=0, 1, . . . , N_{ldpc}−1) and the i^{th }column of the parity check matrix should be a “0” vector. Accordingly, the i^{th }LDPC codeword bit may be regarded as corresponding to the i^{th }column of the parity check matrix.
In the case of the parity check matrix 200 of
In this case, since M number of continuous bits in the information word bits correspond to the same column group of the information word submatrix 210, the information word bits may be formed of M number of continuous bits having a same codeword characteristics. When the parity bits of the LDPC codeword are interleaved by the parity interleaver 121, the parity bits of the LDPC codeword may be formed of M number of continuous bits having same codeword characteristics.
However, regarding the LDPC codeword encoded based on the parity check matrix 300 of
The group interleaver 122 may divide the parityinterleaved LDPC codeword into a plurality of bit groups (or blocks) and rearrange the order of the plurality of bit groups in bit group wise (or bit group unit). That is, the group interleaver 122 may interleave the plurality of bit groups in bit group wise.
When the parity interleaver 121 is omitted depending on cases, the group interleaver 122 may divide the LDPC codeword into a plurality of bit groups and rearrange an order of the bit groups in bit group wise.
The group interleaver 122 divides the parityinterleaved LDPC codeword into a plurality of bit groups by using Equation 19 or Equation 20 presented below.
where N_{group }is the total number of bit groups, X_{j }is the j^{th }bit group, and u_{k }is the k^{th }LDPC codeword bit input to the group interleaver 122. In addition, is the largest integer which is smaller than or equal to k/360.
Since 360 in these equations indicates an example of the interval M at which the pattern of a column group is repeated in the information word submatrix, 360 in these equations can be changed to M.
The LDPC codeword which is divided into the plurality of bit groups may be as shown in
Referring to
Since the LDPC codeword is divided by M number of continuous bits, K_{ldpc }number of information word bits are divided into (K_{ldpc}/M) number of bit groups and N_{ldpc}−K_{ldpc }number of parity bits are divided into (N_{ldpc}−K_{ldpc})/M number of bit groups. Accordingly, the LDPC codeword may be divided into (N_{ldpc}/M) number of bit groups in total.
For example, when M=360 and the length N_{ldpc }of the LDPC codeword is 16200, the number of groups N_{groups }constituting the LDPC codeword is 45(=16200/360), and, when M=360 and the length N_{ldpc }of the LDPC codeword is 64800, the number of bit groups N_{group }constituting the LDPC codeword is 180(=64800/360).
As described above, the group interleaver 122 divides the LDPC codeword such that M number of continuous bits are included in a same group since the LDPC codeword has the same codeword characteristics on the basis of M number of continuous bits. Accordingly, when the LDPC codeword is grouped by M number of continuous bits, the bits having the same codeword characteristics belong to the same group.
In the abovedescribed example, the number of bits constituting each bit group is M. However, this is merely an example and the number of bits constituting each bit group is variable.
For example, the number of bits constituting each bit group may be an aliquot part of M. That is, the number of bits constituting each bit group may be an aliquot part of the number of columns constituting a column group of the information word submatrix of the parity check matrix. In this case, each bit group may be formed of aliquot part of M number of bits. For example, when the number of columns constituting a column group of the information word submatrix is 360, that is, M=360, the group interleaver 122 may divide the LDPC codeword into a plurality of bit groups such that the number of bits constituting each bit group is one of the aliquot parts of 360.
In the following explanation, the number of bits constituting a bit group is M as an example, for the convenience of explanation.
Thereafter, the group interleaver 122 interleaves the LDPC codeword in bit group wise. The group interleaver 122 may group the LDPC codeword into the plurality of bit groups and rearrange the plurality of bit groups in bit group wise. That is, the group interleaver 122 changes positions of the plurality of bit groups constituting the LDPC codeword and rearranges the order of the plurality of bit groups constituting the LDPC codeword in bit group wise.
Here, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise such that bit groups respectively including bits mapped onto a same modulation symbol from among the plurality of bit groups are spaced apart from one another at a predetermined interval.
In this case, the group interleaver 122 may rearrange the order of the plurality of bit groups (or blocks) in bit group wise by considering at least one of the number of rows and columns of the block interleaver 124, the number of bit groups of the LDPC codeword, and the number of bits included in each bit group so that bit groups respectively including bits mapped onto a same modulation symbol are spaced apart from one another at a predetermined interval.
To achieve this, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by using Equation 21 presented below:
Y _{j} =X _{π(0)})(0≦j<N _{group}) (21),
where X_{j }is the j^{th }bit group before group interleaving, and Y_{j }is the j^{th }bit group (or block) after group interleaving. In addition, π(j) is a parameter indicating an interleaving order and is determined based on at least one of a length of an LDPC codeword, a modulation method, and a code rate. That is, π(j) denotes a permutation order for group wise interleaving.
Accordingly, X_{π(0) }is a π(j)^{th }bit group (or block) before group interleaving, and Equation 21 means that the π(j)^{th }bit group before the group interleaving becomes the j^{th }bit group after the group interleaving.
According to an exemplary embodiment, an example of π(j) may be defined as in Tables 15 to 27 presented below.
In this case, π(j) is defined according to a length of an LPDC codeword and a code rate, and a parity check matrix is also defined according to a length of an LDPC codeword and a code rate. Accordingly, when LDPC encoding is performed based on a specific parity check matrix according to a length of an LDPC codeword and a code rate, the LDPC codeword may be interleaved in bit group wise based on π(j) satisfying the same length of the LDPC codeword and code rate.
For example, when the encoder 110 performs LDPC encoding at a code rate of 5/15 to generate an LDPC codeword of a length of 16200, the group interleaver 122 may perform interleaving by using π(j) which is defined according to the length of the LDPC codeword of 16200 and the code rate of 5/15 in Tables 15 to 27 presented below.
For example, when the length of the LDPC codeword is 16200, the code rate is 5/15, and the modulation method (or modulation format) is 256Quadrature Amplitude Modulation (QAM), π(j) may be defined as in Table 15 presented below. In particular, Table 15 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 14.
In the case of Table 15, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{4}, Y_{1}=X_{π(1)}=X_{23}, Y_{2}=X_{π(2)}=X_{3}, . . . , Y_{43}=X_{π(43)}=X_{29}, Y_{44}=X_{π(44)}=X_{28}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 4^{th }bit group (or block) to the 0^{th }bit group, the 23^{rd }bit group to the 1^{st }bit group, the 3^{rd }bit group to the 2^{nd }bit group, . . . , the 29^{th }bit group to the 43^{rd }bit group, and the 28^{th }bit group to the 44^{th }bit group. Herein, the changing the Ath bit group to the Bth bit group means rearranging the order of bit groups so that the Ath bit group is to be the Bth bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 7/15, and the modulation method is 256QAM, π(j) may be defined as in Table 16 presented below. In particular, Table 16 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 5.
In the case of Table 16, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{13}, Y_{1}=X_{π(1)}=X_{16}, Y_{2}=X_{π(2)}=X_{4}, . . . , Y_{43}=X_{π(43)}=X_{41}, Y_{44}=X_{π(44)}=X_{29}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 13^{th }bit group to the 0^{th }bit group, the 16^{th }bit group to the 1^{st }bit group, the 4^{th }bit group to the 2^{nd }bit group, . . . , the 41^{st }bit group to the 43^{rd }bit group, and the 29^{th }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 9/15, and the modulation method is 256QAM, π(j) may be defined as in Table 17 presented below. In particular, Table 17 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 7.
In the case of Table 17, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{5}, Y_{1}=X_{π(1)}=X_{7}, Y_{2}=X_{π(2)}=X_{9}, . . . , Y_{43}=X_{π(43)}=X_{38}, Y_{44}=X_{π(44)}=X_{44}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 5^{th }bit group to the 0^{th }bit group, the 7^{th }bit group to the 1^{st }bit group, the 9^{th }bit group to the 2^{nd }bit group, . . . , the 38^{th }bit group to the 43^{rd }bit group, and the 44^{th }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 11/15, and the modulation method is 256QAM, π(j) may be defined as in Table 18 presented below. In particular, Table 18 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 9.
In the case of Table 18, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{25}, Y_{1}=X_{π(1)}=X_{13}, Y_{2}=X_{π(2)}=X_{4}, . . . , Y_{43}=X_{π(43)}=X_{15}, Y_{44}=X_{π(44)}=X_{36}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 25^{th }bit group to the 0^{th }bit group, the 13^{st }bit group to the 1^{st }bit group, the 4^{th }bit group to the 2^{nd }bit group, . . . , the 15^{th }bit group to the 43^{rd }bit group, and the 36^{th }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 13/15, and the modulation method is 256QAM, π(j) may be defined as in Table 19 presented below. In particular, Table 19 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 11.
In the case of Table 19, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{9}, Y_{1}=X_{π(1)}=X_{13}, Y_{2}=X_{π(2)}=X_{10}, . . . , Y_{43}=X_{π(43)}=X_{35}, Y_{44}=X_{π(44)}=X_{34}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 9^{th }bit group to the 0^{th }bit group, the 13^{th }bit group to the 1^{st }bit group, the 10^{th }bit group to the 2^{nd }bit group, . . . , the 35^{th }bit group to the 43^{rd }bit group, and the 34^{th }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 5/15, and the modulation method is 256QAM, π(j) may be defined as in Table 20 presented below. In particular, Table 20 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 4.
In the case of Table 20, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{8}, Y_{1}=X_{π(1)}=X_{9}, Y_{2}=X_{π(2)}=X_{0}, . . . , Y_{43}=X_{π(43)}=X_{31}, Y_{44}=X_{π(44)}=X_{40}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 8^{th }bit group to the 0^{th }bit group, the 9^{th }bit group to the 1^{st }bit group, the 0^{th }bit group to the 2^{nd }bit group, . . . , the 30 bit group to the 43^{rd }bit group, and the 40^{th }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 7/15, and the modulation method is 256QAM, π(j) may be defined as in Table 21 presented below. In particular, Table 21 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 6.
In the case of Table 21, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{9}, Y_{1}=X_{π(1)}=X_{8}, Y_{2}=X_{π(2)}=X_{4}, . . . , Y_{43}=X_{π(43)}=X_{42}, Y_{44}=X_{π(44)}=X_{40}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 9^{th }bit group to the 0^{th }bit group, the 8^{th }bit group to the 1^{st }bit group, the 4^{th }bit group to the 2^{nd }bit group, . . . , the 42^{nd }bit group to the 43^{rd }bit group, and the 40^{th }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 9/15, and the modulation method is 256QAM, π(j) may be defined as in Table 22 presented below. In particular, Table 22 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 8.
In the case of Table 22, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{14}, Y_{1}=X_{π(1)}=X_{4}, Y_{2}=X_{π(2)}=X_{9}, . . . , Y_{43}=X_{π(43)}=X_{42}, Y_{44}=X_{π(44)}=X_{40}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 14^{th }bit group to the 0^{th }bit group, the 4^{th }bit group to the 1^{st }bit group, the 9^{th }bit group to the 2^{nd }bit group, . . . , the 42^{nd }bit group to the 43rd bit group, and the 40^{th }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 11/15, and the modulation method is 256QAM, π(j) may be defined as in Table 23 presented below. In particular, Table 23 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 10.
In the case of Table 23, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{13}, Y_{1}=X_{π(1)}=X_{28}, Y_{2}=X_{π(2)}=X_{30}, . . . , Y_{43}=X_{π(43)}=X_{31}, Y_{44}=X_{π(44)}=X_{21 }Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 10^{th }bit group to the 0^{th }bit group, the 28^{th }bit group to the 1^{st }bit group, the 30th bit group to the 2^{nd }bit group, . . . , the 31^{st }bit group to the 43^{rd }bit group, and the 21^{st }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 13/15, and the modulation method is 256QAM, π(j) may be defined as in Table 24 presented below. In particular, Table 24 may be applied when LDPC encoding is performed ‘based on the parity check matrix defined by Table 12.
In the case of Table 24, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{21}, Y_{1}=X_{π(1)}=X_{19}, Y_{2}=X_{π(2)}=X_{7}, . . . , Y_{43}=X_{π(43)}=X_{38}, Y_{44}=X_{π(44)}=X_{33}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 21^{st }bit group to the 0^{th }bit group, the 19^{th }bit group to the 1^{st }bit group, the 7^{th }bit group to the 2^{nd }bit group, . . . , the 38^{th }bit group to the 43^{rd }bit group, and the 33^{rd }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 11/15, and the modulation method is 256QAM, π(j) may be defined as in Table 25 presented below. In particular, Table 25 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 9.
In the case of Table 25, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{20}, Y_{1}=X_{π(1)}=X_{16}, Y_{2}=X_{π(2)}=X_{5}, . . . , Y_{43}=X_{π(43)}=X_{43}, Y_{44}=X_{π(44)}=X_{36}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 20^{th }bit group to the 0^{th }bit group, the 16^{th }bit group to the 1^{st }bit group, the 5^{th }bit group to the 2^{nd }bit group, . . . , the 43^{rd }bit group to the 43^{rd }bit group, and the 36^{th }bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 9/15, and the modulation method is 256QAM, π(j) may be defined as in Table 26 presented below. In particular, Table 26 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 8.
In the case of Table 26, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{8}, Y_{1}=X_{π(1)}=X_{4}, Y_{2}=X_{π(2)}=X_{0}, . . . , Y_{43}=X_{π(43)}=X_{41}, Y_{44}=X_{π(44)}=X_{39}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 8^{th }bit group to the 0^{th }bit group, the 4^{th }bit group to the 1^{st }bit group, the 0^{th }bit group to the 2^{nd }bit group, . . . , the 41^{st }bit group to the 43^{rd }bit group, and the 39th bit group to the 44^{th }bit group.
In another example, when the length of the LDPC codeword is 16200, the code rate is 11/15, and the modulation method is 256QAM, π(j) may be defined as in Table 27 presented below. In particular, Table 27 may be applied when LDPC encoding is performed based on the parity check matrix defined by Table 10.
In the case of Table 27, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{28}, Y_{1}=X_{π(1)}=X_{30}, Y_{2}=X_{π(2)}=X_{10}, . . . , Y_{43}=X_{π(43)}=X_{31}, Y_{44}=X_{π(44)}=X_{34}. Accordingly, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by changing the 28^{th }bit group to the 0^{th }bit group, the 30^{th }bit group to the 1^{st }bit group, the 10^{th }bit group to the 2^{nd }bit group, . . . , the 30 bit group to the 43^{rd }bit group, and the 34^{th }bit group to the 44^{th }bit group.
In the abovedescribed examples, the length of the LDPC codeword is 16200 and the code rate is 5/15, 7/15, 9/15, 11/15 and 13/15. However, they are merely examples and the interleaving pattern may be defined differently when the length of the LDPC codeword is 64800 or the code rate has different values.
As described above, the group interleaver 122 may rearrange the order of the plurality of bit groups in bit group wise by using Equation 21 and Tables 15 to 27.
The “jth block of Groupwise Interleaver output” in Tables 15 to 27 indicates the j^{th }bit group output from the group interleaver 122 after interleaving, i.e., group interleaving, and the “π(j)th block of Groupwise Interleaver input” indicates the π(j)^{th }bit group input to the group interleaver 122.
In addition, since the order of the bit groups constituting the LDPC codeword is rearranged by the group interleaver 122 in bit group wise, and then the bit groups are blockinterleaved by the block interleaver 124, which will be described below, the “Order of bit groups to be block interleaved” is set forth in Tables 15 to 27 in relation to π(j).
The LDPC codeword which is groupinterleaved in the abovedescribed method is illustrated in
That is, as shown in
The group twist interleaver 123 interleaves bits in a same group. That is, the group twist interleaver 123 may rearrange an order of bits in a same bit group by changing the order of the bits in the same bit group.
In this case, the group twist interleaver 123 may rearrange the order of the bits in the same bit group by cyclicshifting a predetermined number of bits from among the bits in the same bit group.
For example, as shown in
In addition, the group twist interleaver 123 may rearrange the order of bits in each bit group by cyclicshifting by a different number of bits in each bit group.
For example, the group twist interleaver 123 may cyclicshift the bits included in the bit group Y_{1 }to the right by 1 bit, and may cyclicshift the bits included in the bit group Y_{2 }to the right by 3 bits.
However, the abovedescribed group twist interleaver 123 may be omitted according to circumstances.
In addition, the group twist interleaver 123 is placed after the group interleaver 122 in the abovedescribed example. However, this is merely an example. That is, the group twist interleaver 123 changes only the order of bits in at least one bit group and does not change the order of the bit groups. Therefore, the group twist interleaver 123 may be placed before the group interleaver 122.
The block interleaver 124 interleaves the plurality of bit groups the order of which has been rearranged. The block interleaver 124 may interleave the plurality of bit groups the order of which has been rearranged by the group interleaver 122 in bit group wise (or in a bit group unit). The block interleaver 124 is formed of a plurality of columns each including a plurality of rows, and may interleave by dividing the plurality of rearranged bit groups based on a modulation order determined according to a modulation method.
In this case, the block interleaver 124 may interleave the plurality of bit groups the order of which has been rearranged by the group interleaver 122 in bit group wise. The block interleaver 124 may interleave by dividing the plurality of rearranged bit groups according to a modulation order by using a first part and a second part.
The block interleaver 124 interleaves by dividing each of the plurality of columns into a first part and a second part, writing the plurality of bit groups in the plurality of columns of the first part serially in bit group wise, dividing the bits of the remaining bit groups into groups (or sub bit groups) each including a predetermined number of bits based on the number of the plurality of columns, and writing the sub bit groups in the plurality of columns of the second part serially.
Here, the number of bit groups which are interleaved in bit group wise by the block interleaver 124 may be determined by at least one of the number of rows and columns constituting the block interleaver 124, the number of bit groups, and the number of bits included in each bit group. In other words, the block interleaver 124 may determine bit groups which are to be interleaved in bit group wise considering at least one of the number of rows and columns constituting the block interleaver 124, the number of bit groups, and the number of bits included in each bit group, interleave the bit groups in bit group wise using the first part of the columns, and divide bits of the bit groups not interleaved using the first part of the columns into sub bit groups and interleave the sub bit groups. For example, the block interleaver 124 may interleave at least part of the plurality of bit groups in bit group wise using the first part of the columns, and divide bits of the remaining bit groups into sub bit groups and interleave the sub bit groups using the second part of the columns.
Meanwhile, interleaving bit groups in bit group wise means that the bits included in a same bit group are written in a same column in the present block interleaving. In other words, the block interleaver 124, in case of bit groups which are interleaved in bit group wise, may not divide bits included in a same bit group and write these bits in a same column. However, in case of bit groups which are not interleaved in bit group wise, the block interleaver 124 may divide bits in a same bit group and write these bits in different columns.
Accordingly, the number of rows constituting the first part of the columns is an integer multiple of the number of bits included in one bit group (for example, 360), and the number of rows constituting the second part of the columns may be less than the number of bits included in one bit group.
In addition, in all bit groups interleaved using the first part of the columns, bits included in a same bit group are written in a same column in the first part for interleaving, and in at least one group interleaved using the second part, bits are divided and written in at least two columns of the second part for interleaving.
The specific interleaving method will be described later.
Meanwhile, the group twist interleaver 123 changes only an order of bits in a bit group and does not change an order of bit groups by interleaving. Accordingly, the order of bit groups to be interleaved by the block interleaver 124, that is, the order of bit groups input to the block interleaver 124 may be determined by the group interleaver 122. The order of bit groups to be interleaved by the block interleaver 124 may be determined by π(j) defined in Tables 15 to 27.
As described above, the block interleaver 124 may interleave a plurality of bit groups the order of which has been rearranged in bit group wise by using a plurality of columns each including a plurality of rows.
In this case, the block interleaver 124 may interleave an LDPC codeword by dividing a plurality of columns into at least two parts as described above. For example, the block interleaver 124 may divide each of the plurality of columns into the first part and the second part, and interleave the plurality of bit groups constituting the LDPC codeword.
In this case, the block interleaver 124 may divide each of the plurality of columns into N number of parts (N is an integer greater than or equal to 2) according to whether the number of bit groups constituting the LDPC codeword is an integer multiple of the number of columns constituting the block interleaver 124, and may perform interleaving.
If the number of bit groups constituting the LDPC codeword is an integer multiple of the number of columns constituting the block interleaver 124, the block interleaver 124 may interleave the plurality of bit groups constituting the LDPC codeword in bit group wise without dividing each of the plurality of columns into parts.
The block interleaver 124 may interleave by writing the plurality of bit groups of the LDPC codeword on each of the columns in bit group wise in a column direction, and reading each row of the plurality of columns in which the plurality of bit groups are written in bit group wise in a row direction.
In this case, the block interleaver 124 may interleave by writing bits included in a predetermined number of bit groups, which corresponds to a quotient obtained by dividing the number of bit groups of the LDPC codeword by the number of columns of the block interleaver 124, on each of the plurality of columns serially in a column direction, and reading each row of the plurality of columns in which the bits are written in a row direction.
Hereinafter, a bit group located in the j^{th }position after being interleaved by the group interleaver 122 will be referred to as bit group Y_{j}.
For example, it is assumed that the block interleaver 124 is formed of C number of columns each including R_{1 }number of rows. In addition, it is assumed that the LDPC codeword is formed of N_{group }number of bit groups and the number of bit groups N_{group }is a multiple of C.
In this case, when the quotient obtained by dividing N_{group }number of bit groups constituting the LDPC codeword by C number of columns constituting the block interleaver 124 is A (=N_{group}/C) (A is an integer greater than 0), the block interleaver 124 may interleave by writing A (=N_{group}/C) number of bit groups in the C number of columns serially in a column direction and reading the bits written in the C number of columns in a row direction.
For example, as shown in
Accordingly, the block interleaver 124 interleaves all bit groups constituting the LDPC codeword in bit group wise.
However, when the number of bit groups of the LDPC codeword is not an integer multiple of the number of columns of the block interleaver 124, the block interleaver 124 may divide each column into two (2) parts and interleave a part of the plurality of bit groups of the LDPC codeword in bit group wise, and divide bits of the other or remaining bit groups into sub bit groups and interleave the sub bit groups. In this case, the bits included in the other bit groups, that is, the bits included in the number of groups which correspond to the remainder when the number of bit groups constituting the LDPC codeword is divided by the number of columns are not interleaved in bit group wise, but interleaved by being divided according to the number of columns.
The block interleaver 124 may interleave the LDPC codeword by dividing each of the plurality of columns into two parts.
In this case, the block interleaver 124 may divide the plurality of columns into the first part and the second part based on at least one of the number of columns of the block interleaver 124, the number of bit groups constituting the LDPC codeword, and the number of bits constituting each of the bit groups.
Here, each of the plurality of bit groups may be formed of 360 bits. In addition, the number of bit groups of the LDPC codeword is determined based on the length of the LDPC codeword and the number of bits included in the bit group. For example, when an LDPC codeword in the length of 16200 is divided such that each bit group has 360 bits, the LDPC codeword is divided into 45 bit groups. Alternatively, when an LDPC codeword in the length of 64800 is divided such that each bit group has 360 bits, the LDPC codeword may be divided into 180 bit groups. Further, the number of columns constituting the block interleaver 124 may be determined according to a modulation method. This will be explained below.
Accordingly, the number of rows constituting each of the first part and the second part may be determined based on the number of columns constituting the block interleaver 124, the number of bit groups constituting the LDPC codeword, and the number of bits constituting each of the plurality of bit groups.
In each of the plurality of columns, the first part may be formed of as many rows as the number of bits included in at least one bit group which can be written in a column in bit group wise from among the plurality of bit groups of the LDPC codeword, according to the number of columns constituting the block interleaver 124, the number of bit groups constituting the LDPC codeword, and the number of bits constituting each bit group.
In each of the plurality of columns, the second part may be formed of rows excluding as many rows as the number of bits included in each of at least some bit groups, which can be written in each of the plurality of columns in bit group wise, from among the plurality of bit groups constituting the LDPC codeword. The number rows of the second part may be the same value as a quotient when the number of bits included in all bit groups excluding bit groups corresponding to the first part is divided by the number of columns constituting the block interleaver 124. In other words, the number of rows of the second part may be the same value as a quotient when the number of bits included in the remaining bit groups which are not written in the first part from among bit groups constituting the LDPC codeword is divided by the number of columns.
That is, the block interleaver 124 may divide each of the plurality of columns into the first part including as many rows as the number of bits included in bit groups which can be written in each column in bit group wise, and the second part including the other rows.
Accordingly, the first part may be formed of as many rows as the number of bits included in each bit group, that is, as many rows as an integer multiple of M. However, since the number of codeword bits constituting each bit group may be an aliquot part of M as described above, the first part may be formed of as many rows as an integer multiple of the number of bits constituting each bit group.
In this case, the block interleaver 124 may interleave by writing and reading the LDPC codeword in the first part and the second part in the same method.
The block interleaver 124 may interleave by writing the LDPC codeword in the plurality of columns constituting each of the first part and the second part in a column direction, and reading the plurality of columns constituting the first part and the second part in which the LDPC codeword is written in a row direction.
That is, the block interleaver 124 may interleave by writing all bits included in at least some bit groups, which can be written in each of the plurality of columns in bit group wise, among the plurality of bit groups constituting the LDPC codeword, in each of the plurality of columns of the first part serially, dividing all bits included in the other bit groups and writing the divided bits in the plurality of columns of the second part in a column direction, and reading the bits written in each of the plurality of columns constituting each of the first part and the second part in a row direction.
In this case, the block interleaver 124 may interleave by dividing the other bit groups from among the plurality of bit groups constituting the LDPC codeword based on the number of columns constituting the block interleaver 124.
The block interleaver 124 may interleave by dividing the bits included in the other bit groups by the number of a plurality of columns, writing the divided bits in the plurality of columns constituting the second part in a column direction, and reading the plurality of columns constituting the second part, where the divided bits are written, in a row direction.
That is, the block interleaver 124 may divide the bits included in the other bit groups, from among the plurality of bit groups of the LDPC codeword, by the number of columns, and may write the divided bits in the second part of the plurality of columns serially in a column direction. Here, the bits included in the other bit groups are the same as the bits in the number of bit groups which correspond to the remainder generated when the number of bit groups constituting the LDPC codeword is divided by the number of columns.
For example, it is assumed that the block interleaver 124 is formed of C number of columns each including R_{1 }number of rows. In addition, it is assumed that the LDPC codeword is formed of N_{group }number of bit groups, the number of bit groups N_{group }is not a multiple of C, and A×C+1=N_{group }(A is an integer greater than 0). In other words, it is assumed that when the number of bit groups constituting the LDPC codeword is divided by the number of columns, the quotient is A and the remainder is 1.
In this case, as shown in
That is, in the abovedescribed example, the number of bit groups which can be written in each column in bit group wise is A, and the first part of each column may be formed of as many rows as the number of bits included in A number of bit groups, that is, may be formed of as many rows as A×M number.
In this case, the block interleaver 124 writes the bits included in the bit groups which can be written in each column in bit group wise, that is, A number of bit groups, in the first part of each column in the column direction.
That is, as shown in
As described above, the block interleaver 124 writes the bits included in the bit groups which can be written in the first part of the plurality of columns in bit group wise.
In other words, in the above exemplary embodiment, the bits included in each of bit group (Y_{0}), bit group (Y_{1}), . . . , bit group (Y_{A−1}) may not be divided and all of the bits may be written in the first column, the bits included in each of bit group (Y_{A}), bit group (Y_{A+1}), . . . , bit group (Y_{2A−1}) may not be divided and all of the bits may be written in the second column, . . . , and the bits included in each of bit group (Y_{CAA}), bit group (Y_{CAA+1}), . . . , group (Y_{CA−1}) may not be divided and all of the bits may be written in the last column. As such, all bit groups interleaved using the first part are written such that all bits included in a same bit group are written in a same column of the first part.
Thereafter, the block interleaver 124 divides bits included in bit groups other than the bit groups written in the first part of the plurality of columns from among the plurality of bit groups, and writes the divided bits in the second part of each column in the column direction. In this case, the block interleaver 124 divides the bits included in the other bit groups such that a same number of bits are written in the second part of each column in the column direction. Here, an order of writing bits in the first part and the second part may be reversed. That is, bits may be written in the second part ahead of the first part according to an exemplary embodiment.
In the abovedescribed example, since A×C+1=N_{group}, when the bit groups constituting the LDPC codeword are written in the first part serially, the last bit group Y_{Ngroup−1 }of the LDPC codeword is not written in the first part and remains. Accordingly, the block interleaver 124 divides the bits included in the bit group Y_{Ngroup−1 }into C number of sub bit groups as shown in
The bits divided based on the number of columns may be referred to as sub bit groups. In this case, each of the sub bit groups may be written in each column of the second part. That is, the bits included in the other bit groups may be divided and may form the sub bit groups.
That is, the block interleaver 124 writes the bits in the 1^{st }to R_{2} ^{th }rows of the second part of the 1^{st }column, writes the bits in the 1^{st }to R_{2} ^{th }rows of the second part of the 2^{nd }column, . . . , and writes the bits in the 1^{st }to R_{2} ^{th }rows of the second part of the column C. In this case, the block interleaver 124 may write the bits in the second part of each column in the column direction as shown in
That is, in the second part, bits constituting a bit group may not be written in a same column and may be written in a plurality of columns. In other words, in the above example, the last bit group (Y_{Ngroup−1}) is formed of M number of bits and thus, the bits included in the last bit group (Y_{Ngroup−1}) may be divided by M/C and written in each column. That is, the bits included in the last bit group (Y_{Ngroup−1}) are divided by M/C, forming M/C number of sub bit groups, and each of the sub bit groups may be written in each column of the second part.
Accordingly, in at least one bit group which is interleaved by the second part, the bits included in the at least one bit group are divided and written in at least two columns constituting the second part.
In the abovedescribed example, the block interleaver 124 writes the bits in the second part in the column direction. However, this is merely an example. That is, the block interleaver 124 may write the bits in the plurality of columns of the second part in the row direction. In this case, however, the block interleaver 124 may write the bits in the first part still in the same method as described above, that is, in the column direction.
Referring to
On the other hand, the block interleaver 124 reads the bits written in each row of each part serially in the row direction. That is, as shown in
Accordingly, the block interleaver 124 may interleave a part of the plurality of bit groups constituting the LDPC codeword in bit group wise, and divide bits included the remaining bit groups and interleaved the divided bits. That is, the block interleaver 124 may interleave by writing the LDPC codeword constituting a predetermined number of bit groups from among the plurality of bit groups in the plurality of columns of the first part in bit group wise, dividing bits included the other bit groups from among the plurality of bit groups and writing the divided bits in each of the columns of the second part, and reading the plurality of columns of the first and second parts in the row direction.
As described above, the block interleaver 124 may interleave the plurality of bit groups in the methods described above with reference to
In particular, in the case of
However, the bit group which does not belong to the first part may not be interleaved, as shown in
In
The block interleaver 124 may have a configuration as shown in Tables 28 and 29 presented below:
In the above tables, C (or NO is the number of columns of the block interleaver 124, R_{1 }is the number of rows constituting the first part in each column, and R_{2 }is the number of rows constituting the second part in each column.
Referring to Tables 28 and 29, the number of columns, C, has the same value as a modulation order according to a modulation method, and each of a plurality of columns is formed of as many rows as the number of bits constituting the LDPC codeword divided by the number of a plurality of columns.
For example, when a length N_{ldpc }of an LDPC codeword is 16200 and a modulation method is 256QAM, the block interleaver 124 is formed of 8 columns as the modulation order is 8 in the case of 256QAM, and each column is formed of rows as many as R_{1}+R_{2}=2025 (=16200/8).
Meanwhile, referring to Tables 28 and 29, when the number of bit groups constituting an LDPC codeword is an integer multiple of the number of columns, the block interleaver 124 interleaves without dividing each column. Therefore, R_{1 }corresponds to the number of rows constituting each column, and R_{2 }is 0. In contrast, when the number of bit groups constituting an LDPC codeword is not an integer multiple of the number of columns, the block interleaver 124 interleaves the groups by dividing each column into the first part formed of R_{1 }number of rows, and the second part formed of R_{2 }number of rows.
When the number of columns of the block interleaver 124 is equal to the number of bits constituting a modulation symbol, bits included in a same bit group are mapped onto a single bit of each modulation symbol as shown in Tables 28 and 29.
For example, when N_{ldpc}=16200 and the modulation method is 256QAM, the block interleaver 124 may be formed of eight (8) columns each including 16200 rows. In this case, bits included in each of a plurality of bit groups are written in the eight (8) columns and bits written in a same row in each column are output serially. In this case, since eight (8) bits constitute a single modulation symbol in the modulation method of 256QAM, bits included in a same bit group, that is, bits output from a single column, may be mapped onto a single bit of each modulation symbol. For example, bits included in a bit group written in the 1^{st }column may be mapped onto the first bit of each modulation symbol.
Referring to Tables 28 and 29, the total number of rows of the block interleaver 124, that is, R_{1}+R_{2}, is N_{ldpc}/C.
In addition, the number of rows of the first part, R_{1}, is an integer multiple of the number of bits included in each group, M (e.g., M=360), and may be expressed as └N_{group}/C┘×M, and the number of rows of the second part, R_{2}, may be N_{ldpc}/CR_{1}. Herein, └N_{group}/C┘ is the largest integer which is smaller than or equal to N_{group}/C. Since R_{1 }is an integer multiple of the number of bits included in each group, M, bits may be written in R_{1 }in bit groups wise.
In addition, Tables 18 and 19 show that, when the number of bit groups constituting an LDPC codeword is not an integer multiple of the number of columns, the block interleaver 124 interleaves by dividing each column into two parts.
The length of the LDPC codeword divided by the number of columns is the total number of rows included in the each column. In this case, when the number of bit groups constituting the LDPC codeword is an integer multiple of the number of columns, each column is not divided into two parts for interleaving by the block interleaver 124. However, when the number of bit groups constituting the LDPC codeword is not an integer multiple of the number of columns, each column is divided into two parts for the interleaving by the block interleaver 124.
For example, it is assumed that the number of columns of the block interleaver 124 is identical to the number of bits constituting a modulation symbol, and an LDPC codeword is formed of 64800 bits as shown in Table 28. In this case, each bit group of the LDPC codeword is formed of 360 bits, and the LDPC codeword is formed of 64800/360 (=180) bit groups.
When the modulation method is 16QAM, the block interleaver 124 may be formed of four (4) columns and each column may have 6480014 (=16200) rows.
In this case, since the number of bit groups constituting the LDPC codeword divided by the number of columns is 180/4 (=45), bits can be written in each column in bit group wise without dividing each column into two parts. That is, bits included in 45 bit groups which is the quotient when the number of bit groups constituting the LDPC codeword is divided by the number of columns, that is, 45×360 (=16200) bits can be written in each column.
However, when the modulation method is 256QAM, the block interleaver 124 may be formed of eight (8) columns and each column may have 64800/8 (=8100) rows.
In this case, since the number of bit groups of the LDPC codeword divided by the number of columns is 180/8=22.5, the number of bit groups constituting the LDPC codeword is not an integer multiple of the number of columns. Accordingly, the block interleaver 124 divides each of the eight (8) columns into two parts to perform interleaving in bit group wise.
In this case, since the bits should be written in the first part of each column in bit group wise, the number of bit groups which can be written in the first part of each column in bit group wise is 22, which is the quotient when the number of bit groups constituting the LDPC codeword is divided by the number of columns, and accordingly, the first part of each column has 22×360 (=7920) rows. Accordingly, 7920 bits included in 22 bit groups may be written in the first part of each column.
The second part of each column has as many rows as a value obtained by subtracting the number of rows of the first part from the total number of rows of each column. Accordingly, the second part of each column is formed of 8100−7920 (=180) rows.
In this case, bits included in bit groups which have not been written in the first part are divided and written in the second part of the eight (8) columns.
Since 22×8 (=176) bit groups are written in the first part, the number of bit groups to be written in the second part is 180−176 (=4) (for example, bit group Y_{176}, bit group Y_{177}, bit group Y_{178}, and bit group Y_{179 }from among bit group Y_{0}, bit group Y_{1}, bit group Y_{2}, . . . , bit group Y_{178}, and bit group Y_{179 }constituting the LDPC codeword).
Accordingly, the block interleaver 124 may write the four (4) bit groups which have not been written in the first part and remains from among the plurality of groups constituting the LDPC codeword in the second part of the eight (8) columns serially.
That is, the block interleaver 124 may write 180 bits of the 360 bits included in the bit group Y_{176 }in the 1^{st }row to the 180^{th }row of the second part of the 1^{st }column in the column direction, and write the other 180 bits in the 1^{st }row to the 180^{th }row of the second part of the 2^{nd }column in the column direction. In addition, the block interleaver 124 may write 180 bits of the 360 bits included in the bit group Y_{177 }in the 1^{st }row to the 180^{th }row of the second part of the 3^{rd }column in the column direction, and may write the other 180 bits in the 1^{st }row to the 180^{th }row of the second part of the 4^{th }column in the column direction. In addition, the block interleaver 124 may write 180 bits of the 360 bits included in the bit group Y_{178 }in the 1^{st }row to the 180^{th }row of the second part of the 5^{th }column in the column direction, and may write the other 180 bits in the 1^{st }row to the 180^{th }row of the second part of the 6^{th }column in the column direction. In addition, the block interleaver 124 may write 180 bits of the 360 bits included in the bit group Y_{179 }in the 1^{st }row to the 180^{th }row of the second part of the 7^{th }column in the column direction, and may write the other 180 bits in the 1^{st }row to the 180^{th }row of the second part of the 8^{th }column in the column direction.
Accordingly, bits included in a bit group which has not been written in the first part and remains are not written in a same column in the second part and may be divided and written in a plurality of columns.
Hereinafter, the block interleaver 124 of
In a groupinterleaved LDPC codeword (v_{0}, v_{1}, . . . , v_{N} _{ ldpc } _{−1}), Y_{j }is continuously arranged like V={Y_{0}, Y_{1}, . . . , Y_{N} _{ group } _{−1}}.
An LDPC codeword after group interleaving may be interleaved by the block interleaver 124 as shown in
Input bits v_{i }are written serially in from the first part to the second part in column wise, and then read out serially from the first part to the second part in row wise. That is, data bits v_{i }are written serially into the block interleaver starting from the first part and to the second part in a column direction, and then read out serially from the first part to the second part in a row direction. Accordingly, a plurality of bits included in a same bit group in the first part may be mapped onto a single bit of each modulation symbol. In other words, the bits included in a same bit group in the first part may be mapped onto a plurality of bits respectively included in a plurality of modulation symbols, respectively.
In this case, the number of columns and the number of rows of the first part and the second part of the block interleaver 124 vary according to a modulation format and a length of the LDPC codeword as in Table 25 presented below. That is, the first part and the second part block interleaving configurations for each modulation format and code length are specified in Table 30 presented below. Here, the number of columns of the block interleaver 124 may be equal to the number of bits constituting a modulation symbol. In addition, a sum of the number of rows of the first part, N_{r1 }and the number of rows of the second part, N_{r2}, is equal to N_{ldpc}/N_{C }(herein, N_{C }is the number of columns). In addition, since N_{r1}=└N_{group}/N_{C}┘×360) is a multiple of 360, a multiple of bit groups may be written in the first part.
Hereinafter, an operation of the block interleaver 124 will be explained.
As shown in
respectively.
In addition, the input bit v_{i }(N_{C}×N_{r1}≦i<N_{ldpc}) is written in r_{i }row of c_{i }column of the second part of the block interleaver 124. Herein, c_{i }and r_{i }satisfy
respectively.
An output bit q_{j }(0≦j<N_{ldpc}) is read from c_{j }column of r_{j }row. Herein, r_{j }and C_{j }satisfy
respectively.
For example, when the length N_{ldpc }of an LDPC codeword is 64800 and the modulation method is 256QAM, the order of bits output from the block interleaver 124 may be (q_{0}, q_{1}, q_{2}, . . . , q_{63357}, q_{63358}, q_{63359}, q_{63360}, q_{63361}, . . . , q_{64799})=(v_{O}, v_{7920}, v_{15840}, . . . , v_{47519}, v_{55439}, v_{63359}, v_{63360}, v_{63540}, . . . , v_{64799}). Here, the indexes of the right side of the foregoing equation may be specifically expressed for the eight (8) columns as 0, 7920, 15840, 23760, 31680, 39600, 47520, 55440, 1, 7921, 15841, 23761, 31681, 39601, 47521, 55441, . . . , 7919, 15839, 23759, 31679, 39599, 47519, 55439, 63359, 63360, 63540, 63720, 63900, 64080, 64260, 64440, 64620, . . . , 63539, 63719, 63899, 64079, 64259, 64439, 64619, 64799.
Hereinafter, an interleaving operation of the block interleaver 124 will be explained.
The block interleaver 124 may interleave by writing a plurality of bit groups in a plurality of columns in bit group wise in a column direction, and reading each row of the plurality of columns in which the plurality of bit groups are written in bit group wise in a row direction. In this case, the number of columns constituting the block interleaver 124 may vary according to a modulation method, and the number of rows may be the length of the LDPC codeword divided by the number of columns. For example, when the modulation method is 256QAM, the block interleaver 124 may be formed of eight (8) columns. In this case, when the length N_{ldpc }of the LDPC codeword is 16200, the number of rows is 2025 (=16200/8).
Hereinafter, a method for interleaving the plurality of bit groups in bit group wise by the block interleaver 124 will be explained.
When the number of bit groups constituting an LDPC codeword is an integer multiple of the number of columns, the block interleaver 124 may interleave by writing as many number of bit groups as the number of bit groups constituting the LDPC codeword divided by the number of columns in each column serially in bit group wise.
For example, when the modulation method is 256QAM and the length N_{ldpc }of the LDPC codeword is 16200, the block interleaver 124 may be formed of eight (8) columns each including 2025 rows. In this case, since the LDPC codeword is divided into (16200/360=45) number of bit groups when the length N_{ldpc }of the LDPC codeword is 16200, the number of bit groups (=45) of the LDPC codeword may not be an integer multiple of the number of columns (=8) when the modulation method is 256QAM. That is, a remainder is generated when the number of bit groups of the LDPC codeword is divided by the number of columns.
As described above, when the number of the bit groups constituting the LDPC codeword is not an integer multiple of the number of columns constituting the block interleaver 124, the block interleaver 124 may divide each column into N number of parts (N is an integer greater than or equal to 2) and perform interleaving.
The block interleaver 124 may divide each column into a part which includes rows as many as the number of bits included in a bit group which can be written in each column in bit group wise (that is, the first part) and a part including remaining rows (that is, the second part), and perform interleaving using each of the divided parts.
Here, the part which includes rows as many as the number of bits included in a bit group that can be written in bit group wise, that is, the first part may be composed of rows as many as an integer multiple of M. That is, when the modulation method is 256QAM, each column of the block interleaver 124 consists of 2025 rows, and thus each column of the block interleaver 124 may be composed of the first part including 1800 (=360×5) rows and the second part including 225 (=2025−1800) rows.
In this case, the block interleaver 124, after sequentially writing at least a part of bit groups, which can be written in bit group wise in the plurality of columns, from among the plurality of bit groups constituting the LDPC codeword, may divide and write remaining bit groups at an area other than an area where the at least a part of bit groups are written in the plurality of columns. That is, the block interleaver 124 may write bits included in at least a part of bit groups that can be written in the first part of the plurality of columns in bit group wise, and divide and write the bits included in the remaining bit group in the second part of the plurality of columns.
For example, when the modulation method is 256QAM, as illustrated in
In this case, the block interleaver 124 write bits included in a bit group that can be written in group wise in the first part of each column in a column direction.
That is, the block interleaver 124, as illustrated in
As described above, the block interleaver 124 writes bits included in the bit groups, that can be written in group wise, in the first part of the eight (8) columns in bit group wise.
Thereafter, the block interleaver 124 may divide bits included in remaining bit groups other than the bit groups written in the first part of the eight (8) columns, from among a plurality of groups constituting the LDPC codeword, and write the divided bits in the second part of the eight (8) columns in a column direction. In this case, the block interleaver 124, in order for a same number of bits can be written in the second part of each column, may divide the bits included in the remaining bit groups by the number of columns, and write the divided bits in the second part of the eight (8) columns in a column direction.
For example, as illustrated in
That is, the block interleaver 124, from among 360 bits included in bit group (Y_{40}), may write 225 bits from the 1^{st }row to the 225^{th }row of the second part of the first column in a column direction, and write remaining 135 bits from the 1^{st }row to the 135^{th }row of the second part of the second column in a column direction. In addition, the block interleaver 124, from among 360 bits included in bit group (Y_{41}), may write 90 bits from the 136^{th }row to the 225^{th }row of the second part of the second column in a column direction, write 225 bits from among remaining 270 bits from the 1^{st }row to the 225^{th }row of the second part of the third column in a column direction, and write 45 bits from the 1^{st }row to the 45^{th }row of the second part of the fourth column in a column direction. That is, the block interleaver 124, from among 360 bits included in bit group (Y_{42}), may write 180 bits from the 46^{th }row to the 225^{th }row of the second part of the 4^{th }column in a column direction, and write remaining 180 bits from the 1^{st }row to the 180^{th }row of the second part of the fifth column in a column direction. In addition, the block interleaver 124, from among 360 bits included in bit group (Y_{43}), may write 45 bits from the 181^{st }row to the 225^{th }row of the second part of the fifth column in a column direction, write 225 bits from among remaining 315 bits from the 1st row to the 225^{th }row of the second part of the sixth column in a column direction, and write 90 bits from the 1^{st }row to the 90^{th }row of the second part of the seventh column in a column direction.
In addition, the block interleaver 124, from among 360 bits included in bit group (Y_{44}), may write 135 bits from the 91^{st }row to the 225^{th }row of the second part of the seventh column in a column direction, and write remaining 225 bits from the 1^{st }row to the 225^{th }row of the second part of the eighth column in a column direction.
Accordingly, the bits included in the bit group which remains after the bits are written in the first part may not be written in a same column in the second part, but written over a plurality of columns.
Meanwhile, in the aforementioned example, it is described that the block zinterleaver 124 write bits in the column direction, it is merely exemplary. That is, the block interleaver 124 may write bits in a plurality of columns of the second part in the row direction. In this case, however, the block interleaver 124 may write the bits in the first part still in the same manner as described above, that is, in the column direction.
Referring to
Accordingly, the bits included in bit group (Y_{40}) can be sequentially written from the 1^{st }row of the second part of the first column to the 45^{th }row of the second part of the eighth column, the bits included in bit group (Y_{41}) can be sequentially written from the 46^{th }row of the second part of the first column to the 90^{th }row of the second part of the eighth column, the bits included in bit group (Y_{42}) can be sequentially written from the 91^{st }row of the second part of the first column to the 135^{th }row of the second part of the eighth column, the bits included in bit group (Y_{43}) can be sequentially written from the 136^{th }row of the second part of the first column to the 180^{th }row of the second part of the eighth column, and bits included in the bit group (Y_{44}) can be sequentially written from the 181^{st }row of the second part of the first column to the 225^{th }row of the second part of the eighth column.
Meanwhile, the block interleaver 124 sequentially reads the bits written in each part in the row direction. That is, the block interleaver 124, as illustrated in
As described above, the block interleaver 124 may interleave the plurality of bit groups of the LDPC codeword in the method described above with reference to
The modulator 130 maps the interleaved LDPC codeword onto a modulation symbol. The modulator 130 may demultiplex the interleaved LDPC codeword, modulate the demultiplexed LDPC codeword, and map the modulated LDPC codeword onto a constellation.
In this case, the modulator 130 may generate a modulation symbol using bits included in each of a plurality of bit groups.
In other words, as described above, bits included in different bit groups may be written in different columns of the block interleaver 124, respectively, and the block interleaver 124 reads the bits written in the different column in the row direction. In this case, the modulator 130 generates a modulation symbol by mapping the bits read from the different columns onto respective bits of the modulation symbol. Accordingly, the bits constituting the modulation symbol belong to different bit groups.
For example, it is assumed that the modulation symbol consists of C number of bits. In this case, the bits which are read from each row of C number of columns of the block interleaver 124 may be mapped onto respective bits of the modulation symbol, and thus, these bits of the modulation symbol, i.e., C number of bits, belong to C number of different groups.
Hereinbelow, the above feature will be described.
First, the modulator 130 demultiplexes the interleaved LDPC codeword. To achieve this, the modulator 130 may include a demultiplexer (not shown) to demultiplex the interleaved LDPC codeword.
A demultiplexer (not shown) demultiplexes the interleaved LDPC codeword. The demultiplexer (not shown) performs serialtoparallel conversion with respect to the interleaved LDPC codeword, and demultiplexes the interleaved LDPC codeword into a cell having a predetermined number of bits (or a data cell).
For example, as shown in
In this case, bits having a same index in each of the plurality of substreams may constitute a same cell. Accordingly, the cells may be configured like (y_{0,0}, y_{1,0}, y_{η MOD−1,0})=(q_{0}, q_{1}, q_{η MOD−1}), (y_{0,1}, y_{1,1}, Y_{η MOD−1,1})=(q_{η MOD}, q_{η MOD+1}, . . . , q_{2×η MOD−1}), . . . .
Here, the number of substreams, N_{substreams}, may be equal to the number of bits constituting a modulation symbol, η_{MOD}. Accordingly, the number of bits constituting each cell may be equal to the number of bits constituting a modulation symbol (that is, a modulation order).
For example, when the modulation method is 256QAM, the number of bits constituting the modulation symbol, η_{MOD}, is eight (8), and thus, the number of substreams, N_{substreams}, is eight (8), and the cells may be configured like (y_{0,0}, Y_{1,0}, Y_{2,0}, Y_{3,0}, Y_{4,0}, Y_{5,0}, Y_{6,0}, y_{7,0})=(q_{0}, q_{1}, q_{2}, q_{3}, q_{4}, q_{5}, q_{6}, q_{7}), (y_{0,1}, y_{1,1}, y_{2,1}, y_{3,1}, y_{4,1}, y_{5,1}, y_{6,1}, y_{7,1})=(q_{8}, q_{9}, q_{10}, q_{11}, q_{12}, q_{13}, q_{14}, q_{15}), (y_{0,2}, Y_{1,2}, y_{2,2}, y_{3,2}, y_{4,2}, y_{5,2}, y_{6,2}, y_{7,2})=(q_{16}, q_{17}, q_{18}, q_{19}, q_{20}, q_{21}, q_{22}, q_{23}), . . . .
The modulator 130 may map the demultiplexed LDPC codeword onto modulation symbols.
The modulator 130 may modulate bits (that is, cells) output from the demultiplexer (not shown) in various modulation methods such as 256QAM, etc. For example, when the modulation method is QPSK, 16QAM, 64QAM, 256QAM, 1024QAM, and 4096QAM, the number of bits constituting a modulation symbol, η_{MOD }(that is, the modulation order), may be 2, 4, 6, 8, 10 and 12, respectively.
In this case, since each cell output from the demultiplexer (not shown) is formed of as many bits as the number of bits constituting a modulation symbol, the modulator 130 may generate a modulation symbol by mapping each cell output from the demultiplexer (not shown) onto a constellation point serially. Herein, a modulation symbol corresponds to a constellation point on the constellation.
However, the abovedescribed demultiplexer (not shown) may be omitted according to circumstances. In this case, the modulator 130 may generate modulation symbols by grouping a predetermined number of bits from interleaved bits serially and mapping the predetermined number of bits onto a constellation point. In this case, the modulator 130 may generate a modulation symbol by mapping η_{MOD }number of bits onto a constellation point serially according to a modulation method.
The modulator 130 may modulate by mapping cells output from the demultiplexer (not shown) onto constellation points in a nonuniform constellation (NUC) method.
In the nonuniform constellation method, once a constellation point of the first quadrant is defined, constellation points in the other three quadrants may be determined as follows. For example, when a set of constellation points defined for the first quadrant is X, the set becomes −conj(X) in the case of the second quadrant, becomes conj(X) in the case of the third quadrant, and becomes −(X) in the case of the fourth quadrant.
That is, once the first quadrant is defined, the other quadrants may be expressed as follows:
1 Quarter (first quadrant)=X
2 Quarter (second quadrant)=−conj(X)
3 Quarter (third quadrant)=conj(X)
4 Quarter (fourth quadrant)=−X
When the nonuniform MQAM is used, M number of constellation points may be defined as z={z_{0}, z_{1}, . . . , z_{M−1}}. In this case, when the constellation points existing in the first quadrant are defined as {x_{0}, x_{1}, x_{2}, . . . , x_{M/4−1}}, z may be defined as follows:
from z_{0 }to Z_{M/4−1}=from X_{0 }to x_{M/4 }
from z_{M/4 }to z_{2×M/4−1}=−Conj(from x_{0 }to x_{M/4})
from z_{2×M/4 }to z_{3×M/4−1}=Conj(from x_{0 }to x_{M/4})
from z_{3×M/4 }to z_{4×M/4−1}=−(from x_{0 }to x_{M/4})
Accordingly, the modulator 130 may map bits [y_{0}, . . . , y_{m−1}] output from the demultiplexer (not shown) onto constellation points in the nonuniform constellation method by mapping the output bits onto z_{L }having an index of
An example of constellation which is defined by the above nonuniform constellation method may be expressed as Table 31 below, when the code rate is 5/15, 7/15, 9/15, 11/15 and 13/15.
Table 31 illustrates an example of a constellation defined by the nonuniform 256QAM method, but this is merely exemplary. Constellation points can be defined diversely in the nonuniform 256QAM method, and the constellation points can be defined diversely in other modulation methods such as nonuniform 16QAM, nonuniform 64QAM, nonuniform 1024QAM, nonuniform 4096QAM, and the like.
The interleaving is performed in the abovedescribed method for the following reasons.
When LDPC codeword bits are mapped onto modulation symbols, the bits may have different reliabilities (that is, receiving performance or receiving probability) according to where the bits are mapped onto in the modulation symbols. The LDPC codeword bits may have different codeword characteristics according to the configuration of a parity check matrix. That is, the LDPC codeword bits may have different codeword characteristics according to the number of 1 existing in the column of the parity check matrix, that is, the column degree.
Accordingly, the interleaver 120 may interleave to map LDPC codeword bits having specific codeword characteristics onto specific bits in a modulation symbol by considering both the codeword characteristics of the LDPC codeword bits and the reliability of the bits constituting the modulation symbol.
For example, when the LDPC codeword formed of bit groups X_{0 }to X_{44 }is groupinterleaved based on Equation 21 and Table 16, the group interleaver 122 may output the bit groups in the order of X_{13}, X_{16}, X_{4}, . . . , X_{41}, X_{29}.
In this case, the number of columns of the block interleaver 124 is eight (8) and the number of rows in the first part is 1800 and the number of rows in the second part is 225.
Accordingly, from among the 45 groups constituting the LDPC codeword, five (5) bit groups (X_{13}, X_{16}, X_{4}, X_{12}, X_{44}) may be input to the first part of the first column of the block interleaver 124, five (5) bit groups (X_{15}, X_{8}, X_{14}, X_{0}, X_{3}) may be input to the first part of the second column of the block interleaver 124, five (5) bit groups (X_{30}, X_{20}, X_{35}, X_{21}, X_{10}) may be input to the first part of the third column of the block interleaver 124, five (5) bit groups (X_{6}, X_{19}, X_{17}, X_{26}, X_{39}) may be input to the first part of the fourth column of the block interleaver 124, five (5) bit groups (X_{7}, X_{24}, X_{9}, X_{27}, X_{5}) may be input to the first part of the fifth column of the block interleaver 124, five (5) bit groups (X_{37}, X_{23}, X_{32}, X_{40}, X_{31}) may be input to the first part of the sixth column of the block interleaver 124, five (5) bit groups (X_{38}, X_{42}, X_{34}, X_{25}, X_{36}) may be input to the first part of the seventh column of the block interleaver 124, and five (5) bit groups (X_{2}, X_{22}, X_{43}, X_{33}, X_{28}) may be input to the first part of the eighth column of the block interleaver 124.
In addition, bit group X_{1}, bit group X_{18}, bit group X_{11}, bit group X_{41}, and bit group X_{29 }are input to the second part of the block interleaver 124.
That is, the block interleaver 124 may write 225 bits out of 360 bits included in the bit group (X_{1}) from the 1^{st }row to the 225^{th }row of the second part of the first column in a column direction, and write remaining 135 bits from the 1^{st }row to the 135^{th }row of the second part of the second column in a column direction. The block interleaver 124 may write 90 bits from among 360 bits included in the bit group (X_{18}) from the 136^{th }row to the 225^{th }row of the second part of the second column in a column direction, write 225 bits from among remaining 270 bits from the 1^{st }row to the 225^{th }row of the second part of the third column in a column direction, and write 45 bits from the 1^{st }row to the 45^{th }row of the second part of the fourth column in a column direction. In addition, the block interleaver 124 may write 180 bits out of 360 bits included in the bit group (X_{11}) from the 46^{th }row to the 225^{th }row of the second part of the fourth column in a column direction, and write remaining 180 bits from the 1^{st }row to the 180^{th }row of the second part of the fifth column in a column direction. In addition, the block interleaver 124 may write 45 bits from among 360 bits included in the bit group (X_{41}) from the 181^{st }row to the 225^{th }row of the second part of the fifth column in a column direction, write 225 bits out of remaining 315 bits from the 1^{st }row to the 225^{th }row of the second part of the sixth column in a column direction, and write 90 bits from the 1^{st }row to the 90^{th }row of the second part of the seventh column in a column direction. The block interleaver 124 may write 135 bits from among 360 bits included in the bit group (X_{29}) from the 91^{st }row to the 225^{th }row of the second part of the seventh column in a column direction, and write remaining 225 bits from the 1^{st }row to the 225^{th }row of the second part of the eighth column in a column direction.
In addition, the block interleaver 124 may output the bits inputted to the 1^{st }row to the last row of each column serially, and the bits outputted from the block interleaver 124 may be input to the modulator 130 serially. In this case, the demultiplexer (not shown) may be omitted or the bits may be outputted serially without changing the order of bits inputted to the demultiplexer (not shown). Accordingly, the bits included in each of the bit groups X_{13}, X_{15}, X_{30}, X_{6}, X_{7}, X_{37}, X_{38}, and X_{2 }may constitute a modulation symbol.
As described above, since a specific bit is mapped onto a specific bit in a modulation symbol through interleaving, a receiver side can achieve high receiving performance and high decoding performance.
Hereinafter, a method for determining π(j), which is a parameter used for group interleaving, according to various exemplary embodiments, will be explained. The criteria which needs to be considered is as shown below:
Criteria 1) Determine different interleaving orders based on a modulation method and a code rate.
Criteria 2) Consider functional features of each bit group of an LDPC codeword and functional features of bits constituting a modulation symbol at the same time.
For example, in an LDPC codeword, the leftmost bits may have a better performance than the other bits, and also in a modulation symbol, the leftmost bits may have a better performance that the other bits. In other words, a performance P(y_{i}) of each bit among eight (8) bits (y_{0}, y_{1}, y_{2}, y_{3}, y_{4}, y_{5}, y_{6}, y_{7}) constituting a nonuniform 256QAM symbol is represented as following: P(y_{0})≧P(y_{1})≧P(y_{2})≧P(y_{3})≧P(y_{4})≧P(y_{5})≧P(y_{6})≧P(y_{7}).
Therefore, when a length of an LDPC codeword is 16200, and nonuniform 256QAM (or, referred to as 256NUQ) is used, it is determined which bit from among the eight (8) bits of a 256NUQ symbol is mapped with 45 bit groups, considering characteristics of the code rate and the modulation method simultaneously, and a case of the highest estimated performance is determined by using a density evolution method.
That is, many cases in which 45 bit groups can be mapped onto the eight (8) bits are considered, and a theoretically estimated threshold value for each case is calculated by the density evolution method. Here, the threshold is a signaltonoise ratio (SNR) value and an error probability is ‘0’ in an SNR region higher than the threshold value when an LDPC codeword is transmitted. Therefore, when the LDPC codeword is transmitted in a method of the case in which the threshold value is small from among the many cases for mapping, a high performance can be guaranteed. Designing an interleaver based on the density evolution is a theoretical approach. Therefore, the interleaver should be designed by verifying a code performance based on a really designed parity check matrix and based on cycle distribution, as well as the theoretical approach of the density evolution.
Here, considering the many cases in which 45 bit groups can be mapped onto the eight (8) bits refers to regrouping the bit groups into groups related to the rows of the same degree of the parity check matrix and considering how many groups will be mapped onto the eight (8) 256 QAM bits.
For example, it is assumed that a parity check matrix includes rows having degrees of 16, 10, 3 and 2, and the numbers of bit groups related to each of these rows are 3, 5, 19, 18.
Meanwhile, in the case of the nonuniform 256QAM method, a relative size of a receiving function P(y_{i}) of each bit constituting a modulation symbol is represented as following: P(y_{0})≧P(y_{1})≧P(y_{2})≧P(y_{3})≧P(y_{4})≧P(y_{5})≧P(y_{6})≧P(y_{7}) Here, y_{0}, y_{1 }have the largest impact on a receiving performance of the bits constituting a modulation symbol, and accordingly, which bit group is to be mapped with respect to y_{0}, y_{1 }needs to be determined.
For bit groups which are mapped to y_{0 }and y_{1}, P(y_{0}) and P(y_{1}) are used, and for bit groups which are mapped to other bits (that is, y_{2}, y_{3}, y_{4}, y_{5}, y_{6}, y_{7}), an average probability is used, and the number of cases where bit groups are mapped to y_{0 }and y_{1 }is calculated as shown below.
That is, from among the bit groups mapped to y_{0 }and y_{i}, when x_{i }number of bit groups from among bit groups related to a row of which degree is 16 is selected; w_{1 }number of bit groups from among bit groups related to a row of which degree is 16 is selected; z_{1 }number of bit groups from among bit groups related to a row of which degree is 2 is selected; and l_{1 }number of bit groups from among bit groups related to a row of which degree is 2 is selected, the number of cases can be _{3}C_{x1}+_{5}C_{w1}+_{19}C_{z1}+_{18}C_{l1}.
Accordingly, the number of cases with respect to bit groups mapped with remaining bits can be _{3}C_{(3x1)}+_{5}C_{(5w1)}+_{19}C_{(19z1)}+_{18}C_{(18l1)}.
Then, after estimating functions through density evolution for each case, the case in which the performance would be best will be selected. In other words, to have the best performance through the density evolution, some bit groups are selected from each of the bit groups related to a row of which degree is 16, 10, 3, 2, and it should be determined whether the bit groups need to be mapped with y_{0 }and y_{1}, and then, x_{1}, w_{1}, z_{1}, l_{1 }are determined.
In addition, based on determined x_{1}, w_{1}, z_{1}, l_{1}, which bit group is to be mapped with respect to y_{2}, y_{3}, which has an influence on a receiving performance will be determined.
In this case, with respect to the bit groups mapped with y_{2 }and y_{3}, P(y_{2}) and P(y_{3}) are used, and with respect to the bit groups mapped with other bits (that is, y_{4}, y_{5}, y_{6}, y_{7}), an average probability is used. Accordingly, the number of cases in which the bit groups are mapped with y_{2 }and y_{3 }is calculated as shown below.
In other words, from bit groups mapped with y_{2 }and y_{3}, if x_{2 }is selected from among the bit groups related to a row of which degree is 16, w_{2 }is selected from among the bit groups related to a row of which degree is 10, z_{2 }is selected from among the bit groups related to a row of which degree is 3, and l_{2 }is selected from among the bit groups related to a row of which degree is 2, the number of cases can be _{(3x1)}C_{x2}+_{(5w1)}C_{w2}+_{(19z1)}C_{z2}+_{(18l1)}C_{l2}.
Accordingly, the number of cases for the bit groups mapped with remaining bits can be _{3}C_{(3x1x2)}±_{5}C_{(5w1w2)}±_{19}C_{(19z1z2)}±_{18}C_{(18l1l2)}.
Then, after estimating a performance through density evolution for each case, the case where the performance would be best will be selected. That is, in order to have the best performance through density evolution, by selecting some bit groups from each of the bit groups related to rows of which degree is 16, 10, 3, 2 and determining whether the bit groups are mapped with y_{2 }and y_{3}, the number of _{x2}, w_{2}, z_{2}, l_{2 }will be determined.
Based on the determined x_{2}, w_{2}, z_{2}, l_{2}, by determining how many number of bit groups are mapped with respect to y_{4}, y_{5 }which have an influence over a receiving performance, how many bit groups are mapped with each of the bits constituting a modulation symbol is finally determined from among bit groups related to rows of which degree is 16, 10, 3, and 2.
Accordingly, the case where how many bit groups are mapped with 256QAM bits from each of the bit groups related to rows having each degree has the best performance can be determined, and to satisfy this case, the interleaver 120 which can map a specific group of the LDPC with a specific bit in a modulation symbol will be designed.
Consequently, the group interleaving method according to the present exemplary embodiments may be designed based on the method as described above.
Hereinbelow, the group interleaver design will be described in greater detail.
Meanwhile, as described above, in that each of bit groups constituting the LDPC codeword correspond to each column group of the parity check matrix, a degree of each column group has an effect on decoding performance of the LDPC codeword.
For example, that a degree of column groups is relatively high indicates that there are relatively larger number of parity check equations which are related to bit groups corresponding to column groups, the bit groups which correspond to column groups having a relatively high degree within a parity check matrix formed of a plurality of column groups may have a greater effect on decoding performance of the LDPC codeword rather than bit groups which correspond to column groups having a relatively low degree. In other words, if column groups having a relatively high degree are not mapped appropriately, the performance of the LDPC codeword will be substantially degraded.
Therefore, the group interleaver may be designed such that a bit group(s) having the highest degree, from among the bit groups constituting the LDPC codeword, is interleaved according to the π(j) and mapped to a specific bit of the modulation symbol (or transmission symbol), and the other bit groups not having the highest degree is randomly mapped to the modulation symbol. Under this condition, by observing actual BER/FER performance, the case where the performance of the LDPC codeword is substantially degraded may be avoided.
Hereinbelow, a case where the encoder 110 performs LDPC encoding by using the code rate 5/15 to generate an LDPC codeword having the length of 16200, and constitutes a modulation symbol by using 256NUQ will be described in a greater detail.
In this case, the encoder 110 may perform LDPC encoding based on the parity check matrix comprising the information word submatrix defined by Table 14 and the parity submatrix having a diagonal configuration.
Accordingly, the parity check matrix is formed of 45 column groups, and from among the 45 column groups, 10 column groups have the degree of 10, 7 column groups have the degree of 9, 28 column groups have the degree of 1.
Therefore, with respect to only 10 column groups of which the degree is 10, from among the 45 column groups, several π(j) for the 10 column groups may be generated to satisfy a predetermined condition in the group interleaver design, and π(j) for the other column groups may be remain as a blank. The bit groups which correspond to the other column groups may be set to be mapped randomly onto bits constituting a modulation symbol. Then, π(j) for 10 column groups having the most excellent performance is selected by observing actual BER/FER performance regarding a specific SNR value. By fixing a part of π(j), i.e. π(j) for 10 column groups selected as described above, substantial degradation of the performance of the LDPC codeword may be avoided.
Meanwhile, Table 32 maybe be presented as below Table 321.
In case of Table 32, Equation 21 may be expressed as Y_{3}=X_{π(3)}=X_{6}, Y_{5}=X_{π(5)}=X_{5}, Y_{8}=X_{π(8)}=X_{7}, Y_{25}=X_{π(25)}=X_{9}, Y_{30}=X_{π(30)}=X_{11}, Y_{31}=X_{π(31)}=X_{10}, Y_{34}=X_{π(34)}=X_{13}, Y_{35}=X_{π(35)}=X_{12}, Y_{38}=X_{π(38)}=X_{14}, Y_{41}=X_{π(41)}=X_{8}.
That is, the group interleaver 122 may rearrange the order of the plurality of bit groups by changing the 6^{th }bit group to the 3^{rd }bit group, the 5^{th }bit group to the 5^{th }bit group, the 7^{th }bit group to the 8^{th }bit group, the 9^{th }bit group to the 25^{th }bit group, the 11^{th }bit group to the 30^{th }bit group, the 10^{th }bit group to the 31^{st }bit group, the 13^{th }bit group to the 34^{th }bit group, the 12^{th }bit group to the 35^{th }bit group, the 14^{th }bit group to the 38^{th }bit group, and the 8^{th }bit group to the 41^{st }bit group, and by rearranging randomly the other bit groups.
In a case where some bit groups are already fixed, the aforementioned feature is applied in the same manner. In other words, bit groups which correspond to column groups having a relatively high degree from among the other bit groups which are not fixed may have a greater effect on decoding performance of the LDPC codeword than bit groups which correspond to column groups having a relatively low degree. That is, even in the case where degradation of the performance of the LDPC codeword is prevented by fixing the bit groups having the highest degree, the performance of the LDPC codeword may vary according to a method of mapping the other bit groups. Accordingly, a method of mapping bit groups having the next highest degree needs to be selected appropriately, to avoid the case where the performance is relatively poor.
Therefore, in a case where bit groups having the highest degree are already fixed, bit groups having the next highest degree, from among the bit groups constituting the LDPC codeword, may be interleaved according to the π(j) and mapped to a specific bit of a modulation symbol, and the other bit groups may be randomly mapped. Under this condition, by observing actual BER/FER performance, the case where the performance of the LDPC codeword is substantially degraded may be avoided.
Hereinbelow, a case where the encoder 110 performs LDPC encoding by using the code rate 5/15 to generate an LDPC codeword having the length of 16200, and constitutes a modulation symbol by using 256NUQ will be described in a greater detail.
In this case, the encoder 110 may perform LDPC encoding based on the parity check matrix comprising the information word submatrix defined by Table 14 and the parity submatrix having a diagonal configuration.
Accordingly, the parity check matrix is formed of 45 column groups, and from among the 45 column groups, 10 column groups have the degree of 10, 7 column groups have the degree of 9, and 28 column groups have the degree of 1.
Therefore, in a case where 10 column groups of which the degree is 10 are already fixed as in Table 32, so that, with respect to only 7 column groups of which the degree is 9, from among the other 35 column groups, several π(j) for the 7 column groups may be generated to satisfy a predetermined condition in a group interleaver design, and π(j) for the other column groups may be remain as a blank. The bit groups which correspond to the other column groups may be set to be mapped randomly onto bits constituting a modulation symbol. Then, π(j) for 7 column groups having the most excellent performance is selected by observing actual BER/FER performance regarding a specific SNR value. By fixing a part of π(j), i.e. π(j) for 7 column groups selected as described above, substantial degradation of the performance of the LDPC codeword may be avoided.
In case of Table 34, Equation 21 may be expressed as Y_{0}=X_{π(0)}=X_{4}, Y_{2}=X_{π(2)}=X_{3}, Y_{3}=X_{π(3)}=X_{6}, . . . , Y_{38}=X_{π(38)}=X_{14}, Y_{40}=X_{π(40)}=X_{16}, Y_{41}=X_{π(41)}=X_{8}.
That is, the group interleaver 122 may rearrange the order of the plurality of bit groups by changing the 4^{th }bit group to the 0^{th }bit group, the 3^{rd }bit group to the 2^{nd }bit group, the 6^{th }bit group to the 3^{rd }bit group, . . . , the 14^{th }bit group to the 38^{th }bit group, the 16^{th }bit group to the 40^{th }bit group, and the 8^{th }bit group to the 41^{st }bit group, and by rearranging randomly the other bit groups.
In the exemplary embodiments described above, the case of performing LDPC encoding based on the coding rate of 5/15 and the parity check matrix formed of the information word submatrix defined by Table 14 and the parity submatrix having a diagonal configuration is described, but this is merely exemplary, and even in a case of performing LDPC encoding based on different code rates and different parity check matrix, π(j) can be determined based on the aforementioned method.
The transmitting apparatus 100 may transmit a signal mapped onto a constellation to a receiving apparatus (for example, 1200 of
The demodulator 1210 receives and demodulates a signal transmitted from the transmitting apparatus 100 illustrated in
The value corresponding to the LDPC codeword may be expressed as a channel value for the received signal. There are various methods for determining the channel value, and for example, a method for determining a Log Likelihood Ratio (LLR) value may be the method for determining the channel value.
The LLR value is a log value for a ratio of a probability that a bit transmitted from the transmitting apparatus 100 is 0 and a probability that the bit is 1. In addition, the LLR value may be a bit value which is determined by a hard decision, or may be a representative value which is determined according to a section to which the probability that the bit transmitted from the transmitting apparatus 100 is 0 or 1 belongs.
The multiplexer 1220 multiplexes an output value of the demodulator 1210 and outputs the value to the deinterleaver 1230.
The multiplexer 1220 is an element corresponding to a demultiplexer of
The information regarding whether the demultiplexing operation was performed or not may be provided by the transmitting apparatus 100, or may be predefined between the transmitting apparatus 100 and the receiving apparatus 1200.
The deinterleaver 1230 deinterleaves an output value of the multiplexer 1220 and outputs the values to the decoder 1240.
The deinterleaver 1230 is an element corresponding to the interleaver 120 of the transmitting apparatus 100, and performs an operation corresponding to the interleaver 120. That is, the deinterleaver 1230 deinterleaves an LLR value by performing an interleaving operation of the interleaver 120 inversely.
To do so, the deinterleaver 1230 may include a block deinterleaver 1231, a group twist deinterleaver 1232, a group deinterleaver 1233, and a parity deinterleaver 1234 as shown in
The block deinterleaver 1231 deinterleaves the output value of the multiplexer 1220 and outputs the value to the group twist deinterleaver 1232.
The block deinterleaver 1231 is an element corresponding to the block interleaver 124 provided in the transmitting apparatus 100 and performs an interleaving operation of the block interleaver 124 inversely.
That is, the block deinterleaver 1231 deinterleaves by writing the LLR value output from the multiplexer 1220 in each row in the row direction and reading each column of the plurality of rows in which the LLR value is written in the column direction by using at least one row formed of the plurality of columns.
In this case, when the block interleaver 124 interleaves by dividing each column into two parts, the block deinterleaver 1231 may deinterleave by dividing each row into two parts.
In addition, when the block interleaver 124 writes and read a bit group that does not belong to the first part in the row direction, the block deinterleaver 1231 may deinterleave by writing and reading values corresponding to the bit group that does not belong to the first part in the row direction.
Hereinafter, the block deinterleaver 1231 will be explained with reference to
An input LLR v_{i }(0≦i<N_{ldpc}) is written in r_{i }row and c_{i }column of the block deinterleaver 1231. Herein, c_{i}=(i mod N_{c}) and
On the other hand, an output LLR q_{i}(0≦i<N_{c}×N_{r1}) is read from c_{i }column and r_{i }row of the first part of the block deinterleaver 1231. Herein,
In addition, an output LLR q_{i}(N_{c}×N_{r1}≦i<N_{ldpc}) is read from c_{i }column and r_{i }row of the second part. Herein,
The group twist deinterleaver 1232 deinterleaves an output value of the block deinterleaver 1231 and outputs the value to the group deinterleaver 1233.
The group twist deinterleaver 1232 is an element corresponding to the group twist interleaver 123 provided in the transmitting apparatus 100, and may perform an interleaving operation of the group twist interleaver 123 inversely.
That is, the group twist deinterleaver 1232 may rearrange LLR values of a same bit group by changing the order of the LLR values existing in the same bit group. When the group twist operation is not performed in the transmitting apparatus 100, the group twist deinterleaver 1232 may be omitted.
The group deinterleaver 1233 (or the groupwise deinterleaver) deinterleaves an output value of the group twist deinterleaver 1232 and outputs the value to the parity deinterleaver 1234.
The group deinterleaver 1233 is an element corresponding to the group interleaver 122 provided in the transmitting apparatus 100 and may perform an interleaving operation of the group interleaver 122 inversely.
That is, the group deinterleaver 1233 may rearrange the order of the plurality of bit groups in bit group wise. In this case, the group deinterleaver 1233 may rearrange the order of the plurality of bit groups in bit group wise by applying the interleaving method of Tables 15 to 27 inversely according to a length of the LDPC codeword, a modulation method and a code rate.
The parity deinterleaver 1234 performs parity deinterleaving with respect to an output value of the group deinterleaver 1233 and outputs the value to the decoder 1240.
The parity deinterleaver 1234 is an element corresponding to the parity interleaver 121 provided in the transmitting apparatus 100 and may perform an interleaving operation of the parity interleaver 121 inversely. That is, the parity deinterleaver 1234 may deinterleave LLR values corresponding to parity bits from among the LLR values output from the group deinterleaver 1233. In this case, the parity deinterleaver 1234 may deinterleave the LLR values corresponding to the parity bits inversely to the parity interleaving method of Equation 18.
However, the parity deinterleaver 1234 may be omitted depending on a decoding method and embodiment of the decoder 1240.
Although the deinterleaver 1230 of
For example, when the code rate is 7/15 and the modulation method is 256QAM, the group deinterleaver 1233 may perform deinterleaving based on Table 16.
In this case, bits each of which belongs to each of bit groups X_{13}, X_{15}, X_{30}, X_{6}, X_{7}, X_{37}, X_{38}, X_{2 }may constitute a single modulation symbol. Since one bit in each of the bit groups X_{13}, X_{15}, X_{30}, X_{6}, X_{7}, X_{37}, X_{38}, X_{2 }constitutes a single modulation symbol, the deinterleaver 1230 may map bits onto decoding initial values corresponding to the bit groups X_{13}, X_{15}, X_{30}, X_{6}, X_{7}, X_{37}, X_{38}, X_{2 }based on the received single modulation symbol.
The decoder 1240 may perform LDPC decoding by using an output value of the deinterleaver 1230. To achieve this, the decoder 1240 may include an LDPC decoder (not shown) to perform LDPC decoding.
The decoder 1240 is an element corresponding to the encoder 110 of the transmitting apparatus 100 and may correct an error by performing the LDPC decoding by using LLR values output from the deinterleaver 1230.
For example, the decoder 1240 may perform the LDPC decoding in an iterative decoding method based on a sumproduct algorithm. The sumproduct algorithm is one example of a message passing algorithm, and the message passing algorithm refers to an algorithm which exchanges messages (e.g., LLR values) through an edge on a bipartite graph, calculates an output message from messages input to variable nodes or check nodes, and updates.
The decoder 1240 may use a parity check matrix when performing the LDPC decoding. In this case, a parity check matrix used in the decoding may have the same configuration as that of a parity check matrix used in encoding at the encoder 110, and this has been described above with reference to
In addition, information on the parity check matrix and information on the code rate, etc. which are used in the LDPC encoding may be prestored in the receiving apparatus 1200 or may be provided by the transmitting apparatus 100.
First, an LDPC codeword is generated by LDPC encoding based on a parity check matrix (S1410), and the LDPC codeword is interleaved (S1420).
Then, the interleaved LDPC codeword is mapped onto a modulation symbol (S1430). In this case, a bit included in a predetermined bit group from among a plurality of bit groups constituting the LDPC codeword may be mapped onto a predetermined bit in the modulation symbol.
Each of the plurality of bit groups may be formed of M number of bits, and M may be a common divisor of N_{ldpc }and K_{ldpc }and may be determined to satisfy Q_{ldpc}=(N_{ldpc}−K_{ldpc})/M. Here, Q_{ldpc }is a cyclic shift parameter value regarding columns in a column group of an information word submatrix of the parity check matrix, N_{ldpc }is a length of the LDPC codeword, and K_{ldpc }is a length of information word bits of the LDPC codeword.
In addition, operation S1420 may include interleaving parity bits of the LDPC codeword, dividing the parityinterleaved LDPC codeword by a plurality of bit groups and rearranging the order of the plurality of bit groups in bit group wise, and interleaving the plurality of bit groups the order of which is rearranged.
The order of the plurality of bit groups may be rearranged in bit group wise based on abovedescribed Equation 21.
In this case, π(j) in Equation 21 may be determined based on at least one of a length of an LDPC codeword, a modulation method, and a code rate.
For example, when the LDPC codeword has the length of 16200, the modulation method is 256QAM, and the code rate is 7/15, π(j) may be defined as in Table 16.
As another example, when the LDPC codeword has a length of 16200, the modulation method is 256QAM, and the code rate may be defined as in Table 17.
As still another example, when the length of the LDPC codeword is 16200, the modulation method is 256QAM, and the code rate is 13/15, π(j) can be defined as Table 19.
Meanwhile, at S1420, dividing the LDPC codeword into a plurality of bit groups, rearranging an order of the plurality of bit groups in bit group wise, and interleaving the rearranged plurality of bit groups are included.
Based on Equation 21, the order of the plurality of bit groups can be rearranged in bit group wise.
In this case, in Equation 21, π(j) can be determined based on at least one of the length of the LDPC codeword, the modulation method, and the code rate.
As an example, when the length of the LDPC codeword is 16200, the modulation method is 256QAM, and the code rate is 5/15, π(j) can be determined as Table 15.
Meanwhile, this is merely exemplary, and π(j) may be defined as Tables 1527 described above.
As still another example, π(j), when the length of the LDPC codeword is 16200, the modulation method is 256QAM, and the code rate is 13/15, may be defined as Table 19.
Meanwhile, at S1420, dividing the LDPC codeword into the plurality of bit groups, rearranging the order of the plurality of bit groups in bit group wise, and interleaving the plurality of bit groups of which the order is rearranged are included.
Based on Equation 21, the order of a plurality of bit groups may be rearranged in bit group wise.
In this case, in Equation 21, π(j) may be determined based on at least one of the length of the LDPC codeword, the modulation method, and the code rate.
As an example, when the length of the LDPC codeword is 16200, the modulation method is 256QAM, and the code rate is 5/15, π(j) can be defined as Table 15.
However, this is merely exemplary, and π(j) can be defined as Tables 1527 as described above.
The interleaving the plurality of bit groups of which the order is rearranged may include: writing the plurality of bit groups in each of a plurality of columns in bit group wise in a column direction, and reading each row of the plurality of columns in which the plurality of bit groups are written in bit group wise in a row direction.
In addition, the interleaving the plurality of bit groups may include: serially write, in the plurality of columns, at least some bit groups which are writable in the plurality of columns in bit group wise from among the plurality of bit groups, and then dividing and writing the other bit groups in an area which remains after the at least some bit groups are written in the plurality of columns in bit group wise.
Referring to
The controller 3810 determines an RF channel and a PLP through which a selected service is transmitted. The RF channel may be identified by a center frequency and a bandwidth, and the PLP may be identified by its PLP ID. A specific service may be transmitted through at least one PLP included in at least one RF channel, for each component constituting the specific service. Hereinafter, for the sake of convenience of explanation, it is assumed that all of data needed to play back one service is transmitted as one PLP which is transmitted through one RF channel. In other words, a service has only one data obtaining path to reproduce the service, and the data obtaining path is identified by an RF channel and a PLP.
The RF receiver 3820 detects an RF signal from an RF channel selected by a controller 3810 and delivers OFDM symbols, which are extracted by performing signal processing on the RF signal, to the demodulator 3830. Herein, the signal processing may include synchronization, channel estimation, equalization, etc. Information required for the signal processing may be a value predetermined by the receiving apparatus 3810 and a transmitter according to use and implementation thereof and included in a predetermined OFDM symbol among the OFDM symbols and then transmitted to the receiving apparatus.
The demodulator 3830 performs signal processing on the OFDM symbols, extracts user packet and delivers the user packet to a service reproducer 3740, and the service reproducer 3840 uses the user packet to reproduce and then output a service selected by a user. Here, a format of the user packet may differ depending on a service implementation method and may be, for example, a TS packet or a IPv4 packet.
Referring to
The frame demapper 3831 selects a plurality of OFDM cells constituting an FEC block which belongs to a selected PLP in a frame including OFDM symbols, based on control information from the controller 3833, and provides the selected OFDM cells to the BICM decoder 3834. The frame demapper 3831 also selects a plurality of OFDM cells corresponding to at least one FEC block which includes L1 signaling, and delivers the selected OFDM cells to the BICM decoder 3832 for L1 signaling.
The BICM decoder for L1 signaling 3832 performs signal processing on an OFDM cell corresponding to an FEC block which includes L1 signaling, extracts L1 signaling bits and delivers the L1 signaling bits to the controller 3833. In this case, the signal processing may include an operation of extracting an LLR value for decoding an LDPC codeword and a process of using the extracted LLR value to decode the LDPC codeword.
The controller 3833 extracts an L1 signaling table from the L1 signaling bits and uses the L1 signaling table value to control operations of the frame demapper 3831, the BICM decoder 3834 and the output handler 3835.
The BICM decoder 3834 performs signal processing on the OFDM cells constituting FEC blocks which belong to a selected PLP to extract BBF (Baseband frame)s and delivers the BBFs to the output handler 3835. In this case, the signal processing may include an operation of extracting an LLR value for decoding an LDPC codeword and an operation of using the extracted LLR value to decode the LDPC codeword, which may be performed based on control information output from the controller 3833.
The output handler 3835 performs signal processing on a BBF, extracts a user packet and delivers the extracted user packet to a service reproducer 3840. In this case, the signal processing may be performed based on control information output from the controller 3833.
According to an exemplary embodiment, the output handler 3835 comprises a BBF handler (not shown) which extracts BBP (Baseband packet) from the BBF.
It is assumed that service information on all services selectable by a user are acquired at an initial scan (S4010) prior to the user's service selection (S4020). Service information may include information on a RF channel and a PLP which transmits data required to reproduce a specific service in a current receiving apparatus. As an example of the service information, program specific information/service information (PSI/SI) in an MPEG2TS is available, and normally can be achieved through L2 signaling and an upperlayer signaling.
In the initial scan (S4010), comprehensive information on a payload type of PLPs which are transmitted to a specific frequency band. As an example, there may be information on whether every PLP transmitted to the frequency band includes a specific type of data.
When the user selects a service (S4020), the receiving apparatus transforms the selected service to a transmitting frequency and performs RF signaling detection (S4030). In the frequency transforming operation (S4020), the service information may be used.
When an RF signal is detected, the receiving apparatus performs an L1 signaling extracting operation from the detected RF signal (S4050). Then, the receiving apparatus selects a PLP transmitting the selected service, based on the extracted L1 signaling, (S4060) and extracts a BBF from the selected PLP (S4070). In S4060, the service information may be used.
The operation to extract a BBF (S4070) may include an operation of demapping the transmitted frame and selecting OFDM cells included in a PLP, an operation of extracting an LLR value for LDPC coding/decoding from an OFDM cell, and an operation of decoding the LDPC codeword using the extracted LLR value.
The receiving apparatus, using header information of an extracted BBF, extracts a BBP from the BBF (S4080). The receiving apparatus also uses header information of an extracted BBP to extract a user packet from the extracted BBP (S4090). The extracted user packet is used to reproduce the selected service (S4100). In the BBP extraction operation (S4080) and user packet extraction operation (S4090), L1 signaling information extracted in the L1 signaling extraction operation may be used.
According to an exemplary embodiment, the L1 signaling information includes information on types of a user packet transmitted through a corresponding PLP, and information on an operation used to encapsulate the user packet in a BBF. The foregoing information may be used in the user packet extraction operation (S1480). Specifically, this information may be used in an operation of extracting the user packet which is a reverse operation of encapsulation of the user packet in the BBF. In this case, process for extracting user packet from the BBP (restoring null TS packet and inserting TS sync byte) is same as above description.
A nontransitory computer readable medium, which stores a program for performing the above encoding and/or interleaving methods according to various exemplary embodiments in sequence, may be provided.
The nontransitory computer readable medium refers to a medium that stores data semipermanently rather than storing data for a very short time, such as a register, a cache, and a memory, and is readable by an apparatus. The abovedescribed various applications or programs may be stored in a nontransitory computer readable medium such as a compact disc (CD), a digital versatile disk (DVD), a hard disk, a Bluray disk, a universal serial bus (USB), a memory card, and a read only memory (ROM), and may be provided. Although a bus is not illustrated in the block diagrams of the transmitter apparatus and the receiver apparatus, communication may be performed between each element of each apparatus via the bus. In addition, each apparatus may further include a processor such as a central processing unit (CPU) or a microprocessor to perform the abovedescribed various operations.
At least one of the components, elements or units represented by a block in illustrating the abovedescribed transmitting apparatus and receiving apparatus may be embodied as various numbers of hardware, software and/or firmware structures that execute respective functions described above, according to an exemplary embodiment. For example, at least one of these components, elements or units may use a direct circuit structure, such as a memory, processing, logic, a lookup table, etc. that may execute the respective functions through controls of one or more microprocessors or other control apparatuses. Also, at least one of these components, elements or units may be specifically embodied by a module, a program, or a part of code, which contains one or more executable instructions for performing specified logic functions, and executed by one or more microprocessors or other control apparatuses. Also, at least one of these components, elements or units may further include a processor such as a central processing unit (CPU) that performs the respective functions, a microprocessor, or the like. Two or more of these components, elements or units may be combined into one single component, element or unit which performs all operations or functions of the combined two or more components, elements of units. Also, at least part of functions of at least one of these components, elements or units may be performed by another of these components, element or units. Further, although a bus is not illustrated in the above block diagrams, communication between the components, elements or units may be performed through the bus. Functional aspects of the above exemplary embodiments may be implemented in algorithms that execute on one or more processors. Furthermore, the components, elements or units represented by a block or processing steps may employ any number of related art techniques for electronics configuration, signal processing and/or control, data processing and the like.
The foregoing exemplary embodiments and advantages are merely exemplary and are not to be construed as limiting the present inventive concept. The exemplary embodiments can be readily applied to other types of apparatuses. Also, the description of the exemplary embodiments is intended to be illustrative, and not to limit the scope of the inventive concept, and many alternatives, modifications, and variations will be apparent to those skilled in the art.
Claims (3)
Y _{j} =X _{π(j) }for (0≦j<N _{group}),
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